Bidirectional wireless communication system, wireless communication apparatus, and bidirectional wireless communication method

ABSTRACT

A bidirectional wireless communication system includes: a first wireless communication apparatus for bidirectional communication configured to multiplex a modulated signal obtained by modulating an input signal by a reference carrier signal having a predetermined carrier frequency, and transmit a resultant transmission signal; and a second wireless communication apparatus, having an oscillator configured to oscillate a signal having a free-running oscillation frequency, configured to inject a reception signal received from the first wireless communication apparatus into the oscillator, receive the reception signal while variably controlling the free-running oscillation frequency of the oscillator of the second wireless communication apparatus, detect whether the free-running oscillation frequency of the signal of the oscillator of the second wireless communication apparatus has entered the frequency range up to the injection locking to be frequency-locked with a carrier frequency of the injected reception signal, and generate a communication enable signal.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a Continuation application of U.S. patent application Ser. No.12/923,238 filed Sep. 10, 2010, which in turn claims priority fromJapanese Application No.: 2009-228003, filed on Sep. 30, 2009, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bidirectional wireless communicationsystem, a wireless communication apparatus, and a bidirectional wirelesscommunication method. To be more particular, the present invention isapplicable to a bidirectional wireless data transmission system thatuses different carrier frequencies for transmission and reception infast transmitting signals with carrier frequencies being in a millimeterband of 30 GHz to 300 GHz for carrying movie images and computergraphics, for example, between devices arranged relatively closely toeach other or inside a device.

2. Description of the Related Art

With the recent enormous increase in the amount of information, such asmovie images and computer graphics, demands have been increasing forsystems capable of handling high-speed and large-capacity digitalcommunication regardless of wired or wireless. Wireless datatransmission systems based on millimeter waves have features forimplementing high-speed data transmission. With these high-speed andmass-capacity wireless data transmission systems, the millimeter bandhas been attracting attention as a frequency band of carrier signals tobe used. Accordingly, more and more wireless communication apparatusesfor transmitting modulated signals of the millimeter band at high speedshave come to use.

Especially, use of a wireless communication apparatus, such as onementioned above, for the communication inside a device (thecommunication between chips, between boards, or between modules inside adevice, for example) eliminates the necessity for conductor-basedtransmission paths. Besides, the use of this wireless communicationapparatus enhances the degree of freedom in the arrangement of boardsfor example, thereby lowering the mounting cost and overcoming EMI(Electro-Magnetic Interference) problems that are conspicuous in LVDS(Low Voltage Differential Signaling).

An attempt to build a bidirectional wireless communication system basedon the two wireless communication apparatuses as described above demandsa device realized in low power dissipation in the millimeter band, lowcost, and small size. Especially, a frequency locking method in an RF(radio frequency) circuit is an important factor in any wireless datatransmission system and the circuit scale of such a method heavilydepends on how this method is implemented.

For example, according to bidirectional wireless communication systemswidely used in the third-generation digital cellular system, wirelesscommunication apparatuses each having a transceiver configuration havinga transmitter block and a receiver block both based on frequencysynthesizing are used.

Referring to FIG. 10, there is shown a block diagram illustrating anexemplary configuration of a related-art bidirectional wireless datatransmission system No. 4. The system No. 4 is made up of two wirelesscommunication apparatuses (hereafter referred to as TRX 40 and TRX 50)each using a frequency synthesizer.

The TRX 40 is configured by a reference oscillator 15, a PLL (PhaseLocked Loop) circuit 16, a local oscillation circuit 17, a transmissionsection 18, a reception section 19, a transmission antenna 106, and areception antenna 107. The reference oscillator 15 oscillates a signalhaving a reference oscillation frequency (hereafter referred to as areference oscillation signal) to supply the generated oscillation signalto the PLL circuit 16.

The reference oscillator 15 is connected with the PLL circuit 16. ThePLL circuit 16 has a frequency synthesizer function and generates anoscillation signal having two or more frequencies on the basis of thereference oscillation signal. The PLL circuit 16 is connected with thelocal oscillation circuit 17. On the basis of the oscillation signalhaving two or more frequencies, the local oscillation circuit 17generates a carrier signal having two or more local oscillationfrequencies.

The local oscillation circuit 17 is connected with the transmissionsection 18 and the reception section 19. The transmission section 18 ismade up of a modulation block 101, a baseband amplifier 102, anup-conversion mixer 103, and a power amplifier 105. The modulation block101 modulates entered data DIN1 into a modulated signal SIN1 and outputsthe modulated signal SIN1 to the baseband amplifier 102. The modulationblock 101 is connected with the baseband amplifier 102. The basebandamplifier 102 amplifies the supplied modulated signal SIN1. The basebandamplifier 102 is connected with the up-conversion mixer 103.

The up-conversion mixer 103 is connected with the local oscillationcircuit 17. On the basis of the carrier signal output from the localoscillation circuit 17, the up-conversion mixer 103 up-converts theamplified modulated signal SIN1 and outputs the resultant signal Sout1to the power amplifier 105. The up-conversion mixer 103 is connectedwith the power amplifier 105. The power amplifier 105 amplifies thetransmission signal Sout1. The power amplifier 105 is connected with thetransmission antenna 106, from which the amplified transmission signalSout1 is radiated.

The reception section 19 is made up of a low-noise amplifier 108, adown-conversion mixer 109, a baseband amplifier 119, and a demodulationblock 112. The reception antenna 107 is connected with the low-noiseamplifier 108. The low-noise amplifier 108 amplifies a reception signalSin2 received from the TRX 50. The low-noise amplifier 108 is connectedwith the down-conversion mixer 109.

The down-conversion mixer 109 is connected with local oscillationcircuit 17. On the basis of the carrier signal output from the localoscillation circuit 17, the down-conversion mixer 109 down-converts theamplified reception signal Sin2 and outputs the resultant basebandsignal SOUT2 to the baseband amplifier 119. The down-conversion mixer109 is connected with the baseband amplifier 119. The baseband amplifier119 amplifies the down-converted baseband signal SOUT2. The basebandamplifier 119 is connected with the demodulation block 112. Thedemodulation block 112 demodulates the amplified baseband signal SOUT2,thereby reconstructing the data DOUT2.

The TRX 50 is made up of a frequency offset detection block 27, avariable reference oscillator 28, a PLL circuit 29, a local oscillationcircuit 30, a reception section 31, a transmission section 32, areception antenna 201, and a transmission antenna 211. The frequencyoffset detection block 27 detects a frequency offset from demodulateddata DOUT1 output from the reception section 31 and outputs a resultantfrequency offset detection signal.

The frequency offset detection block 27 is connected with the variablereference oscillator 28. The variable reference oscillator 28 oscillatesa reference oscillation signal to output the oscillated referenceoscillation signal to the PLL circuit 29. The variable referenceoscillator 28 is connected with the PLL circuit 29. The PLL circuit 29has a frequency synthesizer function and generates an oscillation signalhaving two or more frequencies on the basis of the reference oscillationsignal. The PLL circuit 29 is connected with the local oscillationcircuit 30. The local oscillation circuit 30 generates a carrier signalhaving two or more local oscillation frequencies on the basis ofoscillation signal having two or more frequencies.

The reception section 31 is made up of a low-noise amplifier 202, adown-conversion mixer 203, a baseband amplifier 218, and a demodulationblock 205. The reception antenna 201 is connected with the low-noiseamplifier 202. The low-noise amplifier 202 amplifies the receptionsignal Sin1 received from the TRX 40. The low-noise amplifier 202 isconnected with the down-conversion mixer 203. On the basis of carriersignal output from the local oscillation circuit 30, the down-conversionmixer 203 down-converts the amplified reception signal Sin1 and outputsthe resultant baseband signal SOUT1 to the baseband amplifier 218.

The down-conversion mixer 203 is connected with the baseband amplifier218. The baseband amplifier 218 amplifies the down-converted basebandsignal SOUT1. The baseband amplifier 218 is connected with thedemodulation block 205. The demodulation block 205 demodulates theamplified baseband signal SOUT1, thereby reconstructing the data DOUT1.

The transmission section 32 is made up of a modulation block 206, abaseband amplifier 207, an up-conversion mixer 208, and a poweramplifier 210. The modulation block 206 modulates entered data DIN2 andoutputs a resultant modulated signal SIN2 to the baseband amplifier 207.The modulation block 206 is connected with the baseband amplifier 207.The baseband amplifier 207 amplifies the modulated signal SIN2.

The baseband amplifier 207 is connected with the up-conversion mixer208. The up-conversion mixer 208 is connected with the local oscillationcircuit 30. On the basis of the carrier signal output from the localoscillation circuit 30, the up-conversion mixer 208 up-converts theamplified modulated signal SIN2 and outputs the resultant transmissionsignal Sout2 to the power amplifier 210. The up-conversion mixer 208 isconnected with the power amplifier 210. The power amplifier 210amplifies the transmission signal Sout2. The power amplifier 210 isconnected with the transmission antenna 211, from which the amplifiedtransmission signal Sout2 is radiated.

Configuring the bidirectional wireless communication system No. 4 asdescribed above can realize the enhancement and stabilization of thefrequency accuracy of the local oscillation circuit 17 through thefrequency synthesizer based on the PLL circuit 16 in the TRX 40. Inaddition, the enhancement and stabilization of the frequency accuracy ofthe local oscillation circuit 30 can be realized through the frequencysynthesizer based on the PLL circuit 29 in the TRX 50.

The frequency accuracies of the local oscillation circuit 17 and thelocal oscillation circuit 30 depend on the reference oscillator 15 andthe variable reference oscillator 28, respectively. The oscillationfrequencies of the reference oscillator 15 and the variable referenceoscillator 28 are different from each other between the TRX 40 and theTRX 50. Consequently, there resultantly occurs a difference between theoscillation frequencies of the TRX 40 and the TRX 50. In order tosuppress this frequency difference, the frequency offset detection block27 is arranged in the TRX 50 to control the oscillation frequency of thevariable reference oscillator 28 to detect a frequency offset from thedata DOUT1 obtained by demodulating the reception signal Sin1, therebycorrecting the frequency difference.

For example, WCDMA (Wideband Code Division Multiple Access) demands thefrequency accuracy of the variable reference oscillator 28 before thecorrection to be +/−2 ppm and the that after the correction to be +/−0.1ppm. The TRX 40 uses a VCTCXO (voltage control oscillator of temperaturecompensation type) for the reference oscillator 15, thereby realizingthese frequency accuracies in a certain temperature range (−25 degreescentigrade to +75 degrees centigrade, for example). The TRX 50 uses apilot part of the reception signal Sin1 to detect a frequency offset tocontrol the frequency control terminal voltage of the VCTCXO, therebyexecuting the fine tuning of the frequency. Thus, according to thefrequency synthesizing, the absolute and relative accuracies offrequency can be controlled.

Further, a method is proposed in which, instead of the local oscillationcircuit 17 and the local oscillation circuit 30 that use the PLL circuit16 and the PLL circuit 29, for example, a free-running local oscillatorof injection lock type using locking pull-in phenomenon may be used forthe locking of transmission and reception frequencies. This phenomenonis described in Razavi, “A Study of Injection Locking and Pulling inOscillators,” IEEE Journal of Solid-state Circuits, Vol. 39, No. 9,September 2004, (hereinafter referred to as Non-Patent Document 1), forexample. Injection locking is widely known as a phenomenon in which,when a signal having a frequency in the proximity of an oscillationfrequency is injected in an oscillator, the oscillation frequency ofthis oscillator is pulled in the frequency of the injected signal. To bemore specific, a reference carrier signal is multiplexed with amodulated signal to be injected in a free-running local oscillator,thereby causing a pull-in phenomenon. This free-running local oscillatoreliminates the necessity for the PLL circuit 16 and the PLL circuit 29,thereby realizing circuit simplification.

As for a wireless communication system based on the free-running localoscillator described above, Japanese Patent Laid-open No. 2007-158851(page 5, FIG. 2) (hereinafter referred to as Patent Document 1)discloses a bidirectional wireless communication apparatus, abidirectional wireless communication system, and a bidirectionalwireless communication method. According to this bidirectional wirelesscommunication system, when wireless modulated signals betweenbidirectional wireless communication apparatuses are transmitted orreceived, each bidirectional wireless communication apparatus isconfigured by transmission means, band separation means, injection lockoscillation means, and reception control means. The transmission meanstransmits a wireless modulated signal generated by multiplying anintermediate frequency band modulated signal obtained by modulating asignal to be transmitted to the mate of communication into anintermediate frequency band by a local oscillation signal.

The band separation means band-separates the harmonic component of thelocal oscillation signal having frequency N·fLO and the wirelessmodulated signal component from the received reception signal. Theinjection lock oscillation means divides the harmonic component of thelocal oscillation signal separated by the band separation means by 1/Nto generate a local oscillation signal having frequency fLO.

On the premise of this, the reception control means multiplies thewireless modulated signal separated by the band separation means by theharmonic component of the local oscillation signal generated by theinjection lock oscillation means, thereby down-converting a resultantsignal into the intermediate frequency band. Configuring thebidirectional wireless communication system as described above can lowerthe frequency of the local oscillation signal, so that the manufacturingprocesses of the bidirectional wireless communication system can besimplified, eventually leading to a significant cost reduction.

In addition, Japanese Patent Laid-open No. 2007-228499 (page 7, FIG. 2)(hereinafter referred to as Patent Document 2) discloses a signalprocessing apparatus and method as an example of arranging a wirelesscommunication apparatus of injection lock type inside a device.According to the disclosed signal processing apparatus, two or moresignal processing blocks for processing data signals that are signals ofpredetermined data are arranged in one housing. Of these two or moresignal processing blocks, a predetermined signal processing block hasinjection lock oscillation means.

In locking with an injection signal, the injection lock oscillationmeans oscillates such that a carrier signal for modulating ordemodulating a data signal to be transmitted to any one of the two ormore signal processing blocks in a wireless manner is generated. Theinjection signal (or a clock signal) comes from another signalprocessing block or the oscillator in a wired manner. The data signal istransmitted to any one of the two or more signal processing blocks in awireless manner.

Each signal processing block has communication means. On the premisethereof, the communication means, by use of a carrier signal, modulatesdata signal to be transmitted to any one of the two or more signalprocessing blocks in a wireless manner or demodulates a data signalcoming from any one of the two or more signal processing blocks in awireless manner. Configuring each signal processing block as describedabove can efficiently execute data signal transmission and reception ina wireless manner within the housing of the apparatus.

SUMMARY OF THE INVENTION

It should be noted here however that the related-art bidirectionalwireless data transmission system No. 4 presents the following problems.

(i) According to the bidirectional wireless data transmission system No.4 shown in FIG. 10, the TRX 40 must have the PLL circuit 16 forfrequency synthesizer and the TRX 50 must have the frequency offsetdetection block 27 and the PLL circuit 29 for frequency synthesizer.However, this configuration increases the circuit scale of each of theTRX 40 and the TRX 50.

(ii) Employment of frequency synthesizing makes it difficult to correctoscillation frequency differences between the TRX 40 and the TRX 50 if afrequency offset exceeds a detection range.

(iii) The wireless communication apparatuses using the free-runninglocal oscillator based on injection locking as shown in Patent Document1 or Non-Patent Document 1 limit a lockable range. The lockable rangeherein denotes a frequency range in which the oscillation frequency of asignal oscillated by the free-running local oscillator reaches injectionlocking. In this lockable range, the oscillation frequency of a signalof the oscillator concerned locks with the frequency of an injectedsignal due to the injection lock pull-in phenomenon. Therefore, it isdemanded for these wireless communication apparatuses to be designedsuch that the free-running oscillation frequency of the bidirectionallocal oscillation circuit falls within the lockable range. However,fluctuations and the like in the manufacturing of the free-running localoscillator may push the free-running oscillation frequency out of theinjection locking range.

(iv) In building a bidirectional wireless communication system, thefrequency locking must be shared between the TRX 40 and the TRX 50. Ifthe injection locking is executed independently in the TRX 40 and theTRX 50, a sequence for determining the locking with each other getscomplicated.

(v) According to the signal processing apparatus described in PatentDocument 2 above, a method is employed in which clock signals aresupplied to two or more signal processing blocks in a wired manner anddata is transmitted in a wireless manner. However, in this method, alocal oscillation signal injection-locked in the clock signal must beused for the modulation and demodulation of wireless signals. Thisconfiguration must lay the wiring for clock signal transmission insidethe housing of each signal processing apparatus.

Therefore, the present embodiment addresses the above-identified andother problems associated with related-art methods and apparatuses andsolves the addressed problems by providing a bidirectional wirelesscommunication system, a wireless communication apparatus, andbidirectional wireless communication method that are configured suchthat the frequency locking circuit and so on can be implemented bycircuits simpler than the circuit containing a PLL circuit by contrivingthe configurations and frequency locking state confirmation method ofthe wireless communication apparatuses of the transmission side and thereception side.

In carrying out the invention and according to one embodiment thereof,there is provided a bidirectional wireless communication system. Herelet a phenomenon in which injecting a signal having a frequency in theproximity of an oscillation frequency into an oscillator causes theoscillation frequency of the oscillator to be pulled in the frequency ofthe injected signal be injection locking. Let another phenomenon inwhich, when the oscillation frequency of the signal oscillated by theoscillator enters a frequency range up to the injection locking, theoscillation frequency of the signal of the oscillator is locked with thefrequency of the injected signal by the pull-in phenomenon of theinjection locking be frequency locking. This bidirectional wirelesscommunication system has a first wireless communication apparatus forbidirectional communication configured to multiplex a modulated signalobtained by modulating an input signal by a reference carrier signalhaving a predetermined carrier frequency, and transmit a resultanttransmission signal; and a second wireless communication apparatus,having an oscillator for oscillating a signal having a free-runningoscillation frequency, configured to inject a reception signal receivedfrom the first wireless communication apparatus into the oscillator,receive the reception signal while variably controlling the free-runningoscillation frequency of the oscillator of the second wirelesscommunication apparatus, detect whether the free-running oscillationfrequency of the signal of the oscillator of the second wirelesscommunication apparatus has entered the frequency range up to theinjection locking to be frequency-locked with a carrier frequency of theinjected reception signal, and generate a communication enable signal.In the above-mentioned configuration, if the free-running oscillationfrequency of the signal of the oscillator of the second wirelesscommunication apparatus is found frequency-locked with the carrierfrequency of the injected reception signal, then the second wirelesscommunication apparatus transmits the communication enable signal to thefirst wireless communication apparatus.

According to the first bidirectional wireless communication systemassociated with the invention, the first wireless communicationapparatus multiplexes a modulated signal obtained by modulating an inputsignal by a reference carrier signal having a predetermined carrierfrequency and transmits a resultant transmission signal. The secondwireless communication apparatus injects a reception signal receivedfrom the first wireless communication apparatus into the oscillator,receives the reception signal while variably controlling thefree-running oscillation frequency of the oscillator, detects whetherthe free-running oscillation frequency of the signal of the oscillatorhas entered the frequency range up to injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal, and generates a communication enable signal. If the free-runningoscillation frequency is found frequency-locked with the carrierfrequency of the injected reception signal, the second wirelesscommunication apparatus transmits the generated communication enablesignal to the first wireless communication apparatus. Consequently, thefirst wireless communication apparatus becomes ready for detecting (orrecognizing) on the basis of the communication enable signal that thefrequency locking with the second wireless communication apparatus hasbeen completed and both the wireless communication apparatus is in acommunicable state.

In carrying out the invention and according to another embodimentthereof, there is provided a first wireless communication apparatuspracticed as another embodiment of the invention. Here, let a phenomenonin which injecting a signal having a frequency in the proximity of anoscillation frequency into an oscillator causes the oscillationfrequency of the oscillator to be pulled in the frequency of theinjected signal be injection locking. Let another phenomenon in which,when the oscillation frequency of the signal oscillated by theoscillator enters a frequency range up to the injection locking, theoscillation frequency of the signal of the oscillator is locked with thefrequency of the injected signal by the pull-in phenomenon of theinjection locking be frequency locking. Then, wireless communication isexecuted with a mate wireless communication apparatus that has anoscillator for oscillating a signal having a free-running oscillationfrequency in which a received reception signal is injected in theoscillator, receives the reception signal while variably controlling thefree-running oscillation frequency of the oscillator, detects whetherthe free-running oscillation frequency of the signal of the oscillatorhas entered a frequency range up to the injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal, and generates a communication enable signal. This first wirelesscommunication apparatus has a transmission section configured tomultiplex a modulated signal obtained by modulating an input signal witha reference carrier signal having a predetermined carrier frequency andtransmit a resultant transmission signal to the mate wirelesscommunication apparatus; and a reception section configured to receivethe communication enable signal from the mate wireless communicationapparatus if the free-running oscillation frequency of the signal of theoscillator of the mate wireless communication apparatus is found enteredthe frequency range up to the injection locking to be frequency-lockedwith the carrier frequency of the injected reception signal.

According to the first wireless communication apparatus associated withthe embodiment, the transmission section multiplexes a modulated signalobtained by modulating an input signal by the reference carrier signalhaving a predetermined carrier frequency and transmits a resultanttransmission signal to the mate wireless communication apparatus. Onthis premise, if the free-running oscillation frequency of theoscillator of the mate wireless communication apparatus has beenfrequency-locked with the carrier frequency of the injected receptionsignal, the reception section is ready for receiving a communicationenable signal from the mate wireless communication apparatus.Consequently, the first wireless communication apparatus can detect (orrecognize) on the basis of the communication enable signal that thefrequency locking with the mate wireless communication apparatus hasbeen completed and both the wireless communication apparatuses are in acommunicable state.

In carrying out the invention and according to still another embodimentthereof, there is provided a second wireless communication apparatus.Here, let a phenomenon in which injecting a signal having a frequency inthe proximity of an oscillation frequency into an oscillator causes theoscillation frequency of the oscillator to be pulled in the frequency ofthe injected signal be injection locking. Let another phenomenon inwhich, when the oscillation frequency of the signal oscillated by theoscillator enters a frequency range up to the injection locking, theoscillation frequency of the signal of the oscillator is locked with thefrequency of the injected signal by the pull-in phenomenon of theinjection locking be frequency locking. Then, wireless communication isexecuted with a wireless communication apparatus on the transmissionside that multiplexes a modulated signal obtained by modulating an inputsignal by a reference carrier signal having a predetermined carrierfrequency, transmits a resultant transmission signal, and receives atleast a communication enable signal. This second wireless communicationapparatus has a reception section configured to have an oscillator foroscillating a signal having a free-running oscillation frequency, injecta reception signal received from the wireless communication apparatus onthe transmission side into the oscillator, and receives the receptionsignal while variably controlling the free-running oscillation frequencyof the oscillator; a signal generation block configured to detectwhether the free-running oscillation frequency of the signal of theoscillator has entered the frequency range up to the injection lockingto be frequency-locked with the carrier frequency of the injectedreception signal and generate a communication enable signal; and atransmission section configured to transmit the communication enablesignal generated by the signal generation block to the wirelesscommunication apparatus on the transmission side.

According to the second wireless communication apparatus associated withthe embodiment, the reception section injects a reception signalreceived from the wireless communication apparatus on the transmissionside into the oscillator and receives the reception signal whilevariably controlling the free-running oscillation frequency of thisoscillator. The signal generation block detects whether the free-runningoscillation frequency of the signal of the oscillator has entered thefrequency range up to the injection locking to be frequency-locked withthe carrier frequency of the injected reception signal and generates acommunication enable signal. On this premise, if the free-runningoscillation frequency is found by the signal generation block to havebeen frequency-locked, then the transmission section transmits thegenerated communication enable signal to the wireless communicationapparatus on the transmission side. Consequently, the wirelesscommunication apparatus on the reception side can detect (or recognize)that the frequency locking with the mate wireless communicationapparatus has been completed and both the wireless communicationapparatuses are in a communicable state.

In carrying out the invention and according to yet another embodimentthereof, there is provided a first bidirectional wireless communicationmethod. Here, let a phenomenon in which injecting a signal having afrequency in the proximity of an oscillation frequency into anoscillator causes the oscillation frequency of the oscillator to bepulled in the frequency of the injected signal be injection locking. Letanother phenomenon in which, when the oscillation frequency of thesignal oscillated by the oscillator enters a frequency range up to theinjection locking, the oscillation frequency of the signal of theoscillator is locked with the frequency of the injected signal by thepull-in phenomenon of the injection locking be frequency locking. Thisfirst bidirectional wireless communication method has the steps of: in afirst wireless communication apparatus for bidirectional communication,multiplexing a modulated signal obtained by modulating an input signalby a reference carrier signal having a predetermined carrier frequencyand transmitting a resultant transmission signal; in a second wirelesscommunication apparatus, having an oscillator configured to oscillate asignal having a free-running oscillation frequency, injecting areception signal received from the first wireless communicationapparatus into the oscillator, receiving the reception signal whilevariably controlling the free-running oscillation frequency of theoscillator of the second wireless communication apparatus, detectingwhether the free-running oscillation frequency of the signal of theoscillator of the second wireless communication apparatus has enteredthe frequency range up to the injection locking to be frequency-lockedwith a carrier frequency of the injected reception signal, andgenerating a communication enable signal; and if the free-runningoscillation frequency of the signal of the oscillator of the secondwireless communication apparatus is found frequency-locked with thecarrier frequency of the injected reception signal, transmitting thecommunication enable signal to the first wireless communicationapparatus.

In carrying out the invention and according to a different embodimentthereof, there is provided a second bidirectional wireless communicationsystem. Here, let a phenomenon in which injecting a signal having afrequency in the proximity of an oscillation frequency into anoscillator causes the oscillation frequency of the oscillator to bepulled in the frequency of the injected signal be injection locking. Letanother phenomenon in which, when the oscillation frequency of thesignal oscillated by the oscillator enters a frequency range up to theinjection locking, the oscillation frequency of the signal of theoscillator is locked with the frequency of the injected signal by thepull-in phenomenon of the injection locking be frequency locking. Thissecond bidirectional wireless communication system has a first wirelesscommunication apparatus for bidirectional communication configured, whenmultiplexing a modulated signal obtained by modulating an input signalby a reference carrier signal having a predetermined carrier frequency,and transmitting a resultant transmission signal, to transmit thetransmission signal while variably controlling the carrier frequency ofthe reference carrier signal; and a second wireless communicationapparatus, having an oscillator configured to oscillate a signal havinga free-running oscillation frequency, configured to inject a receptionsignal received from the first wireless communication apparatus into theoscillator, detect whether the free-running oscillation frequency of thesignal of the oscillator of the second wireless communication apparatushas entered the frequency range up to the injection locking to befrequency-locked with a carrier frequency of the injected receptionsignal, generate a communication enable signal, and if the free-runningoscillation frequency of the signal of the oscillator of the secondwireless communication apparatus is found frequency-locked with thecarrier frequency of the injected reception signal, transmit thecommunication enable signal to the first wireless communicationapparatus.

According to the second bidirectional wireless communication systemassociated with the invention, when multiplexing a modulated signalobtained by modulating an input signal by the reference carrier signalhaving a predetermined carrier frequency and transmitting a resultanttransmission signal, the first wireless communication apparatustransmits this transmission signal while variably controlling thecarrier frequency of the reference carrier signal. The second wirelesscommunication apparatus injects a reception signal received from thefirst wireless communication apparatus into the oscillator, detectswhether the free-running oscillation frequency of the oscillator hasentered the frequency range up to the injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal, and generates a communication enable signal. If the free-runningoscillation frequency of the signal of the oscillator is foundfrequency-locked with the carrier frequency of the injected receptionsignal, the second wireless communication apparatus transmits thegenerated communication enable signal to the first wirelesscommunication apparatus. Consequently, the first wireless communicationapparatus can detect (or recognize) on the basis of the communicationenable signal that the frequency locking with the second wirelesscommunication apparatus has been completed and both the wirelesscommunication apparatuses are in a communicable state.

In carrying out the invention and according to a still differentembodiment thereof, there is provided a third wireless communicationapparatus. Here, let a phenomenon in which injecting a signal having afrequency in the proximity of an oscillation frequency into anoscillator causes the oscillation frequency of the oscillator to bepulled in the frequency of the injected signal be injection locking. Letanother phenomenon in which, when the oscillation frequency of thesignal oscillated by the oscillator enters a frequency range up to theinjection locking, the oscillation frequency of the signal of theoscillator is locked with the frequency of the injected signal by thepull-in phenomenon of the injection locking be frequency locking. Then,wireless communication is executed with a mate wireless communicationapparatus that has an oscillator for oscillating a signal having afree-running oscillation frequency in which a received reception signalis injected in the oscillator, receives the reception signal whilevariably controlling the free-running oscillation frequency of theoscillator, detects whether the free-running oscillation frequency ofthe signal of the oscillator has entered a frequency range up to theinjection locking to be frequency-locked with the carrier frequency ofthe injected reception signal, and generates a communication enablesignal. This third wireless communication apparatus has a transmissionsection configured, when multiplexing a modulated signal obtained bymodulating an input signal by a reference carrier signal having apredetermined carrier frequency and transmitting a resultanttransmission signal to the mate wireless communication apparatus, totransmit the transmission signal while variably controlling the carrierfrequency of the reference carrier signal; and a reception sectionconfigured to receive a communication enable signal from the matewireless communication apparatus when the free-running oscillationfrequency of the signal of the oscillator of the mate wirelesscommunication apparatus has entered the frequency range up to theinjection locking to be frequency-locked with the carrier frequency ofthe injected reception signal.

According to the third wireless communication apparatus associated withthe embodiment, when multiplexing a modulated signal obtained bymodulating an input signal by the reference carrier signal havingpredetermined carrier frequency and transmitting a resultanttransmission signal to the mate wireless communication apparatus, thetransmission section transmits the transmission signal while variablycontrolling the carrier frequency of the reference carrier signal. Onthis premise, the reception section receives a communication enablesignal from the mate wireless communication apparatus when thefree-running oscillation frequency of the oscillator of the matewireless communication apparatus has frequency-locked with the injectedreception signal. Consequently, the third wireless communicationapparatus can detect (or recognize) on the basis of the communicationenable signal that the frequency locking with the mate wirelesscommunication apparatus has been completed and both the wirelesscommunication apparatuses are in a communicable state.

In carrying out the invention and according to a yet differentembodiment thereof, there is provided a fourth wireless communicationapparatus. Here, let a phenomenon in which injecting a signal having afrequency in the proximity of an oscillation frequency into anoscillator causes the oscillation frequency of the oscillator to bepulled in the frequency of the injected signal be injection locking. Letanother phenomenon in which, when the oscillation frequency of thesignal oscillated by the oscillator enters a frequency range up to theinjection locking, the oscillation frequency of the signal of theoscillator is locked with the frequency of the injected signal by thepull-in phenomenon of the injection locking be frequency locking. Then,wireless communication is executed with a wireless communicationapparatus on the transmission side that transmits a resultanttransmission signal while variably controlling the carrier frequency ofthe reference carrier signal and receives at least a communicationenable signal when multiplexing a modulated signal obtained bymodulating an input signal by a reference carrier signal having apredetermined carrier frequency and transmitting a resultanttransmission signal. This fourth wireless communication apparatus has areception section, having an oscillator for oscillating a signal havinga free-running oscillation frequency, configured to inject a receptionsignal received from the wireless communication apparatus on thetransmission side into the oscillator and receive the reception signal;a signal generation block configured to detect whether the free-runningoscillation frequency of the signal of the oscillator has entered afrequency range up to the injection locking to be frequency-locked withthe carrier frequency of the injected reception signal and generate acommunication enable signal; and a transmission section configured totransmit the communication enable signal generated by the signalgeneration block to the wireless communication apparatus on thetransmission side.

According to the fourth wireless communication apparatus associated withthe embodiment, the reception section, having an oscillator foroscillating a signal having a free-running oscillation frequency,injects a reception signal received from the wireless communicationapparatus on the transmission side into the oscillator and receive thereception signal; a signal generation block detects whether thefree-running oscillation frequency of the signal of the oscillator hasentered a frequency range up to the injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal and generate a communication enable signal; and on this premise,if the free-running oscillation frequency of the signal of theoscillator is found frequency locked with the carrier frequency of theinjected reception signal, a transmission section transmits thecommunication enable signal generated by the signal generation block tothe wireless communication apparatus on the transmission side.Consequently, the fourth wireless communication apparatus can detect (orrecognize) on the basis of the communication enable signal that thefrequency locking with the mate wireless communication apparatus hasbeen completed and both the wireless communication apparatuses are in acommunicable state.

In carrying out the invention and according to a separate embodimentthereof, there is provided a second bidirectional wireless communicationmethod. Here, let a phenomenon in which injecting a signal having afrequency in the proximity of an oscillation frequency into anoscillator causes the oscillation frequency of the oscillator to bepulled in the frequency of the injected signal be injection locking. Letanother phenomenon in which, when the oscillation frequency of thesignal oscillated by the oscillator enters a frequency range up to theinjection locking, the oscillation frequency of the signal of theoscillator is locked with the frequency of the injected signal by thepull-in phenomenon of the injection locking be frequency locking. Thissecond bidirectional wireless communication method has the steps of:when multiplexing a modulated signal obtained by modulating an inputsignal by a reference carrier signal having a predetermined carrierfrequency and transmitting a resultant transmission signal,transmitting, by a first wireless communication apparatus forbidirectional communication, the transmission signal while variablycontrolling the carrier frequency of the reference carrier signal;injecting, by a second wireless communication apparatus having anoscillator for oscillating a signal having a free-running oscillationfrequency, a reception signal received from the first wirelesscommunication apparatus into the oscillator of the second wirelesscommunication apparatus, detecting whether the free-running oscillationfrequency of the signal of the oscillator of the second wirelesscommunication apparatus has entered the frequency range up to theinjection locking to be frequency-locked with the carrier frequency ofthe injected reception signal, and generating a communication enablesignal; and if the free oscillation frequency of the signal of theoscillator is found frequency-locked with the carrier frequency of theinjected reception signal, transmitting the communication enable signalto the first wireless communication apparatus.

According to the first bidirectional wireless communication system andthe first bidirectional wireless communication method, the secondwireless communication apparatus detects that the free-runningoscillation frequency of a signal oscillated by the oscillator hasentered a frequency range up to injection locking to be frequency-lockedwith the carrier frequency of the injected reception signal. When thisfrequency locking is detected, the second wireless communicationapparatus transmits a communication enable signal to the first wirelesscommunication apparatus.

The above-mentioned configuration allows the first wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the secondwireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, when data is transmitted from the first wirelesscommunication apparatus to the second wireless communication apparatusafter the frequency locking, the second wireless communication apparatuscan reconstruct the data on the basis of the signal having theoscillation frequency after the frequency locking. Besides, as comparedwith a related-art circuit having a PLL circuit, a frequency lockingcircuit and the like can be each configured with a simpler circuit.

According to the first wireless communication apparatus associated withthe embodiment, when the frequency locking of the free-runningoscillation frequency of the oscillator on the reception side with thecarrier frequency of the injected reception is detected, the firstwireless communication apparatus receives a communication enable signalfrom the mate wireless communication apparatus.

The above-mentioned configuration allows the first wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the matewireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, when data is transmitted from this wireless communicationapparatus to the mate wireless communication apparatus after thefrequency locking, the mate wireless communication apparatus canreconstruct the data on the basis of the signal having the oscillationfrequency after the frequency locking. Besides, as compared with arelated-art circuit having a PLL circuit, a frequency locking circuitand the like can be each configured with a simpler circuit.

According to the second wireless communication apparatus associated withthe embodiment, the second wireless communication apparatus can detectthat the free-running oscillation frequency of the oscillator hasentered the frequency range up to injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal. When this frequency locking is detected, the transmissionsection transmits a communication enable signal to the wirelesscommunication apparatus on the transmission side.

The above-mentioned configuration allows the second wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the matewireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, receiving data from the mate wireless communicationapparatus after the frequency locking, the wireless communicationapparatus concerned can reconstruct the received data on the basis ofthe signal having the oscillation frequency after the frequency locking.Besides, as compared with a related-art circuit having a PLL circuit, afrequency locking circuit and the like can be each configured with asimpler circuit.

According to the second bidirectional wireless communication system andthe second bidirectional wireless communication method, a modulatedsignal obtained by modulating an input signal is multiplexed with areference carrier signal having a predetermined carrier frequency and aresultant transmission signal is transmitted. In this transmission, thetransmission signal is transmitted while the first wirelesscommunication apparatus variably controls the carrier frequency of thereference carrier signal. When the second wireless communicationapparatus detects that the free-running oscillation frequency of thesignal oscillated by the oscillator has entered the frequency range upto injection locking to be frequency-locked with the carrier frequencyof the injected reception signal, a communication enable signal istransmitted to the first wireless communication apparatus.

The above-mentioned configuration allows the first wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the secondwireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, when data is transmitted from the first wirelesscommunication apparatus to the second wireless communication apparatusafter the frequency locking, the second wireless communication apparatuscan reconstruct the data on the basis of the signal having theoscillation frequency after the frequency locking. Besides, as comparedwith a related-art circuit having a PLL circuit, a frequency lockingcircuit and the like can be each configured with a simpler circuit.

According to the third wireless communication apparatus associated withthe embodiment, a transmission section is arranged that transmits atransmission signal while variably controlling the carrier frequency ofa reference carrier signal. When the third wireless communicationapparatus detects that the free-running oscillation frequency of theoscillator on the reception side has entered the frequency range up toinjection locking to be frequency-locked with the carrier frequency ofthe injected reception signal, the third wireless communicationapparatus receives a communication enable signal from the mate wirelesscommunication apparatus.

The above-mentioned configuration allows the third wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the matewireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, when data is transmitted from the wireless communicationapparatus concerned to the mate wireless communication apparatus afterthe frequency locking, the mate wireless communication apparatus canreconstruct the data on the basis of the signal having the oscillationfrequency after the frequency locking. Besides, as compared with arelated-art circuit having a PLL circuit, a frequency locking circuitand the like can be each configured with a simpler circuit.

According to the fourth wireless communication apparatus associated withthe embodiment, a signal generation block is arranged for detectingwhether the free-running oscillation frequency of the signal of theoscillator has entered the frequency range up to injection locking to befrequency-locked with the carrier frequency of the injected receptionsignal and generating a communication enable signal. When the frequencylocking is found between the free-running oscillation frequency of theoscillator on the reception side and the carrier frequency of theinjected reception signal, the transmission section transmits thegenerated communication enable signal to the wireless communicationapparatus on the transmission side.

The above-mentioned configuration allows the fourth wirelesscommunication apparatus to detect (or recognize) on the basis of thecommunication enable signal that the frequency locking with the matewireless communication apparatus has been completed and both thewireless communication apparatuses are in a communicable state.Consequently, when data is received from the mate wireless communicationapparatus after the frequency locking, the wireless communicationapparatus concerned can reconstruct the data on the basis of the signalhaving the oscillation frequency after the frequency locking. Besides,as compared with a related-art circuit having a PLL circuit, a frequencylocking circuit and the like can be each configured with a simplercircuit.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from thefollowing description of embodiments with reference to the accompanyingdrawings in which:

FIG. 1 is a block diagram illustrating an exemplary configuration of abidirectional wireless data transmission system No. 1 practiced as afirst embodiment of the invention;

FIGS. 2A and 2B are block diagrams illustrating exemplary internalconfigurations of a control block and a frequency locking detectionblock;

FIG. 3 is a graph indicative of an exemplary relation between injectionsignal output value and free-running oscillation frequency;

FIGS. 4A and 4B are graphs indicative of examples of control onfree-running oscillation frequency in the control block;

FIGS. 5A and 5B are sequence charts indicative of a wirelesscommunication example in the bidirectional wireless data transmissionsystem practiced as the first embodiment of the invention;

FIG. 6 is a block diagram illustrating an exemplary configuration of abidirectional wireless data transmission system No. 2 practiced as asecond embodiment of the invention;

FIG. 7 is a block diagram illustrating an exemplary configuration of abidirectional wireless data transmission system No. 3 practiced as athird embodiment of the invention;

FIGS. 8A and 8B are block diagrams illustrating exemplary internalconfigurations of a control block and a frequency locking detectionblock;

FIGS. 9A and 9B are sequence charts indicative of a wirelesscommunication example in the bidirectional wireless data transmissionsystem No. 3; and

FIG. 10 is a block diagram illustrating an exemplary configuration of abidirectional wireless data transmission system No. 4 related to arelated art example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of embodimentsthereof, namely, a bidirectional wireless data transmission system, awireless communication apparatus, and a bidirectional wirelesscommunication method, with reference to the accompanying drawings. Theexplanation will be made in the following order:

(1) the first embodiment (an exemplary configuration and an exemplarywireless communication of the bidirectional wireless data transmissionsystem No. 1);

(2) the second embodiment (an exemplary configuration and an exemplarywireless communication of the bidirectional wireless data transmissionsystem No. 2); and

(3) the third embodiment (an exemplary configuration and an exemplarywireless communication of the bidirectional wireless data transmissionsystem No. 3).

The First Embodiment

Now, referring to FIG. 1, a bidirectional wireless data transmissionsystem No. 1 practiced as the first embodiment of the invention will bedescribed. The bidirectional wireless data transmission system No. 1shown in FIG. 1 constitutes one example of a bidirectional wirelesscommunication system and transmits signals of a millimeter band havingfrequencies 30 GHz to 300 GHz at high speeds. Millimeter band signalscarry movie images, computer graphics, and the like between devicesarranged in proximity and inside each device. This is applicable to anasymmetrical wireless data transmission system for realizing frequencylocking based on injection locking by use of different carrierfrequencies in transmission and reception.

This injection locking herein denotes a phenomenon in which, when asignal having a frequency in the proximity of an oscillation frequencyis injected in an oscillator, the oscillation frequency of thisoscillator is pulled into the frequency of the injected signal. Thefrequency locking herein denotes a phenomenon in which, when theoscillation frequency of a signal oscillated by an oscillator gets in afrequency range up to the injection locking, the oscillation frequencyof the signal of the oscillator locks with the frequency of the injectedsignal due to the above-mentioned injection locking pull-in phenomenon.

The bidirectional wireless data transmission system No. 1 is composed oftwo wireless communication apparatuses; a bidirectional wirelesscommunication apparatus on the transmission side configuring one exampleof a first wireless communication apparatus and a second bidirectionalwireless communication apparatus on the reception side configuring oneexample of a second wireless communication apparatus, for example. Thebidirectional wireless communication apparatus on the transmission sideis hereafter abbreviated to a TRX1. The second bidirectional wirelesscommunication apparatus on the reception side is hereafter abbreviatedto a TRX2. In this example, an oscillator 23 is arranged on thereceiving TRX2 to vary free-running oscillation frequency f2 of thisoscillator 23 to capture free-running oscillation frequency f2 into thefrequency range, thereby detecting frequency locking. A bidirectionalfrequency locking state can be confirmed by transmitting and receivingsignals in the millimeter band by use of this detection as a trigger.

The TRX1 multiplexes modulated signal SIN1 obtained by modulating aninput signal (hereafter referred to as data DIN1) with reference carriersignal Sr having predetermined carrier frequency f1 and transmitsresultant transmission signal Sout1. For example, the TRX1 is composedof a transmission section 11, a reception section 12, an oscillator 13,a transmission antenna 106, and a reception antenna 107.

For the oscillator 13, a single voltage control oscillator for localoscillation is used. In this example, the oscillator 13 is sharably usedbetween the transmission section 11 and the reception section 12. Thetransmission section 11 executes transmission processing on the basis ofreference carrier signal Sr having carrier frequency f1 (oscillationfrequency) oscillated by the oscillator 13. The reception section 12executes reception processing on the basis of local oscillation signalS1′ having local oscillation frequency f1′ obtained by multiplyingreference carrier signal Sr oscillated by the oscillator 13. In thisexample, one oscillator 13 simultaneously controls carrier frequency f1of the transmission section 11 and local oscillation frequency f1′ ofthe reception section 12. This control processing can lock carrierfrequency f1 with free-running oscillation frequency f2 at all the timesof transmission and reception between the wireless communicationapparatuses TRX1 and TRX2 if frequency locking is established betweenthe wireless communication apparatuses TRX1 and TRX2.

The transmission section 11 is composed of a modulation block 101, abaseband amplifier 102, an up-conversion mixer 103, an adder 104, and apower amplifier 105. The modulation block 101 receives data DIN1,modulates this data DIN1, and outputs modulated signal SIN1. Themodulation block 101 is connected with the baseband amplifier 102. Thebaseband amplifier 102 amplifies modulated signal SIN1.

The baseband amplifier 102 is connected with the up-conversion mixer103. The up-conversion mixer 103 executes up-conversion processing (themultiplication processing for frequency conversion) on amplifiedmodulated signal SIN1 (baseband signal) and reference carrier signal Srhaving carrier frequency f1 and outputs a resultant frequency convertedsignal.

The up-conversion mixer 103 is connected with the adder 104. The adder104 outputs transmission signal Sout1 obtained by adding (multiplexing)reference carrier signal Sr having carrier frequency f1 to theup-converted frequency-converted signal. Reference carrier signal Sr isadded to this frequency-converted signal in order to make it easy toexecute the injection locking based on reference carrier signal Sr inthe TRX2.

Obviously, reference carrier signal Sr having unmodulated carrierfrequency f1 may be transmitted to the TRX2 without adding referencecarrier signal Sr to the frequency converted signal. The transmissiontiming may be an injection locking control period between the TRX1 andthe TRX2 and the frequency locking based on the injection locking may beexecuted in this injection locking control period. The injection lockingcontrol period herein denotes a period in which injection locking isexecuted such that reference carrier signal Sr having carrier frequencyf1 on the transmission side is matched with local oscillation signal S1based on free-running oscillation frequency f2 on the reception side.

The adder 104 is connected with the power amplifier 105. the poweramplifier 105 amplifies transmission signal Sout1 after addition andoutputs amplified transmission signal Sout1 from the transmissionantenna 106. The transmission antenna 106 receives transmission signalSout1 and radiates electromagnetic waves. Consequently, the transmissionsection 11 is ready for transmitting transmission signal Sout1 withreference carrier signal Sr having predetermined carrier frequency f1multiplied with modulated signal SIN1 obtained by modulating data DIN1to the communication mate TRX2.

The reception section 12 is composed of a low-noise amplifier 108, adown-conversion mixer 109, a frequency multiplier 110, a bandpass filter111, and a demodulation block 112. The reception antenna 107 isconnected with the low-noise amplifier 108. The low-noise amplifier 108amplifies reception signal Sin2 received by the reception antenna 107.Reception signal Sin2 contains a carrier signal that is two times ashigh as free-running oscillation frequency f2. Reception signal Sin2contains enable signal SEN coming from the TRX2 at the time of injectionlocking.

The low-noise amplifier 108 is connected with the down-conversion mixer109. The down-conversion mixer 109 is connected with the frequencymultiplier 110. The frequency multiplier 110, connected to theoscillator 13, outputs local oscillation signal S1′ of 2×f1 obtained bymultiplying carrier frequency f1 by 2 to the down-conversion mixer 109.The down-conversion mixer 109 down-converts (subtracts) reception signalSin2 on the basis of local oscillation signal S1′ output from thefrequency multiplier 110, thereby demodulating baseband signal SOUT2(demodulated signal).

The down-conversion mixer 109 is connected with the bandpass filter 111.The bandpass filter 111 passes baseband signal SOUT2 containing enablesignal SEN at the time of injection locking. The bandpass filter 111 isconnected with the demodulation block 112. The demodulation block 112demodulates baseband signal SOUT2 and outputs data DOUT2 that containsenable signal SEN.

When the TRX1 is configured as described above, free-running oscillationfrequency f2 of local oscillation signal S1 of the oscillator 23 of theTRX2 gets in the frequency range up to the injection locking andfrequency-locks with carrier frequency f1 of injected reception signalSin1 in the reception section 12. Then, upon the establishment of thefrequency locking, the TRX1 is ready for receive enable signal SEN fromthe TRX2. Consequently, the frequency locking with the communicationmate TRX2 is completed on the basis of enable signal SEN and the TRX1 isready for detecting (recognizing) a communication enabled state.

In addition, the TRX2 has a single local oscillator of free-runningoscillating injection locking type (hereafter simply referred to as anoscillator 23). The oscillator 23 oscillates local oscillation signal S1having free-running oscillation frequency f2. For the oscillator 23, avoltage control oscillator is used.

The TRX2 injects received reception signal Sin1 into the oscillator 23and receives reception signal Sin1 while variably controllingfree-running oscillation frequency f2 of the oscillator 23. The TRX2detects whether free-running oscillation frequency f2 of localoscillation signal S1 has entered the frequency range up to theinjection locking to be frequency-locked with carrier frequency f1 ofinjected reception signal Sin1. If the frequency locking is detected,the TRX2 generates communication enable signal (hereafter simplyreferred to as an enable signal SEN).

In the TRX2, the oscillator 23 is also sharably used between a receptionsection 21 and a transmission section 22. The reception section 21 isconfigured to execute reception processing on the basis of localoscillation signal S1 having free-running oscillation frequency f2 afterinjection locking oscillated by the oscillator 23. The transmissionsection 22 is configured to execute transmission processing on the basisof carrier signal Sr′ obtained by multiplying local oscillation signalS1 after injection locking oscillated by the oscillator 23. In thisexample, one oscillator 23 simultaneously controls both free-runningoscillation frequency f2 of the reception section 21 and carrierfrequency fr′ of the transmission section 22. This control processingcan lock carrier frequency f1 with free-running oscillation frequency f2at all the times of transmission and reception between the TRX1 and theTRX2 if frequency locking is established between the TRX1 and the TRX2.

In addition to the oscillator 23, the TRX2 is composed of the receptionsection 21, the transmission section 22, a control block 24, a frequencylocking detection block 25, the reception antenna 201, and thetransmission antenna 211. The control block 24 and the frequency lockingdetection block 25 constitute one example of a signal generation unit.

The reception section 21 injects reception signal Sin1 received from theTRX1 into the oscillator 23 and receives reception signal Sin1 whilevariably controlling free-running oscillation frequency f2 of theoscillator 23. For example, the reception section 21 is composed of thelow-noise amplifier 202, the down-conversion mixer 203, a lowpass filter204, and the demodulation block 205.

The reception antenna 201 is connected with the low-noise amplifier 202.The low-noise amplifier 202 amplifies reception signal Sin1 received bythe reception antenna 201. Reception signal Sin1 contains carrierfrequency f1. The low-noise amplifier 202 is connected with thedown-conversion mixer 203 and the oscillator 23. The down-conversionmixer 203 is connected with the oscillator 23. Into the oscillator 23,amplified reception signal Sin1 is injected.

The down-conversion mixer 203 outputs baseband signal SOUT1 obtained byexecuting down-conversion processing (subtraction) on reception signalSin1 on the basis of local oscillation signal S1 having free-runningoscillation frequency f2 output from the oscillator 23. Thedown-conversion mixer 203 is connected with the lowpass filter 204. Thelowpass filter 204 removes the low-frequency component from basebandsignal SOUT1 to pass baseband signal SOUT1 removed of the low-frequencycomponent. The lowpass filter 204 is connected with the frequencylocking detection block 25 and the demodulation block 205. Thedemodulation block 205 demodulates baseband signal SOUT1 to output dataDOUT1.

The oscillator 23 is connected with the control block 24 thatconstitutes a part of the signal generation unit. The control block 24reception-controls reception signal Sin1 while variably controllingfree-running oscillation frequency f2 of the oscillator 23 withreception signal Sin1 injected. The frequency locking detection block 25constitutes a part of the signal generation unit and detects whetherfree-running oscillation frequency f2 of local oscillation signal S1 hasbeen frequency-locked with carrier frequency f1 of reception signalSin1. If the frequency locking is detected, the frequency lockingdetection block 25 generates enable signal SEN. Enable signal SEN isoutput to the control block 24 and the transmission section 22 when theoscillator 23 is frequency-locked by injection locking.

If frequency locking of free-running oscillation frequency f2 is foundlocked with carrier frequency f1 of injected reception signal Sin1 inthe frequency locking detection block 25, the transmission section 22transmits enable signal SEN to the TRX1. The transmission section 22 iscomposed of the modulation block 206, the baseband amplifier 207, theup-conversion mixer 208, a frequency multiplier 209, and the poweramplifier 210.

The modulation block 206 receives data DIN2, modulates received dataDIN2, and outputs modulated signal SIN2. In this example, free-runningoscillation frequency f2 of the oscillator 23 is frequency-locked withcarrier frequency f1 of injected reception signal Sin1. In the frequencylocking, the modulation block 206 modulates enable signal SEN outputfrom the frequency locking detection block 25 to output modulated signalSIN2 containing enable signal SEN.

The modulation block 206 is connected with the baseband amplifier 207.The baseband amplifier 207 amplifies the modulated signal SIN2. Thebaseband amplifier 207 is connected with the up-conversion mixer 208.The up-conversion mixer 208 and the above-mentioned oscillator 23 areconnected with the frequency multiplier 209. The frequency multiplier209 outputs carrier frequency fr′=2·f2 obtained by multiplyingfree-running oscillation frequency f2 by 2 to the up-conversion mixer208.

The up-conversion mixer 208 executes up-conversion processing(multiplication processing for frequency conversion) on amplifiedmodulated signal SIN2 and carrier signal Sr′ having carrier frequencyfr′ and outputs resultant transmission signal Sout2. The up-conversionmixer 208 is connected with the power amplifier 210. The power amplifier210 amplifies up-converted transmission signal Sout2 and outputsamplified transmission signal Sout2 to the transmission antenna 211. Thetransmission antenna 211 receives transmission signal Sout2 and radiateselectromagnetic waves. Consequently, the transmission section 22 isready for transmitting transmission signal Sout2 with modulated signalSIN2 containing enable signal SEN multiplied by carrier signal Sr′having predetermined carrier frequency fr′ to communication mate TRX1.

Also, in carrier frequency f1 in the transmission section 11 of the TRX1and carrier frequency fr′ in the transmission section 22 of the TRX2,relation M/N is set between carrier frequency f1 of the TRX1 and carrierfrequency fr′=2·f1 of the TRX2. It should be noted that M and N aregiven integers. For example, if carrier frequency f1 in the TRX1 is setto 60 GHz, then carrier frequency fr′ in the TRX2 is set to 120 GHz.Namely, f1:fr′=60:120=M:N (2:1) in this example.

Obviously, carrier signal Sr′ obtained by dividing local oscillationsignal S1 having free-running oscillation frequency f2 may be used. Forexample, if carrier frequency f1 in the TRX1 is set to 60 GHz, thencarrier frequency fr′ in the TRX2 is set to 30 GHz. Namely,f1:fr′=60:30=M:N (2:1) in this example.

The following describes exemplary internal configurations of the controlblock 24 and the frequency locking detection block 25 with reference toFIGS. 2A and 2B. In order to variably control free-running oscillationfrequency f2 of the oscillator 23, the control block 24 is composed ofan up-counter 41 and a digital/analog converter (hereafter referred toas a DA conversion 42). The up-counter 41 up-counts the number of pulsesof clock signal CLK for example on the basis of start signal Start andoutputs oscillation control data Dc and, on the basis of stop signalStop, stops outputting oscillation control data Dc. The up-counter 41 isconnected with the DA converter 42.

The DA converter 42 digital-to-analog converts oscillation control dataDc to generate analog VCO control voltage Vc. VCO control voltage Vc isoutput to the oscillator 23. If VCO control voltage Vc gets higher thana certain reference voltage, the oscillator 23 decreases free-runningoscillation frequency f2. If VCO control voltage Vc gets lower than acertain reference voltage, the oscillator 23 increases free-runningoscillation frequency f2.

The control block 24 repeatedly increases or decreases free-runningoscillation frequency f2 of the oscillator 23 within a frequency rangeup to injection locking, thereby executing variable tuning. This allowsvariable control on free-running oscillation frequency f2 of theoscillator 23 in which reception signal Sin1 has been injected. Thereception section 21 is configured as described above. In this receptionsection 21, free-running oscillation frequency f2 of local oscillationsignal S1 by the oscillator 23 can be forcibly injected brought into thefrequency range up to injection locking, thereby forciblyfrequency-locking free-running oscillation frequency f2 with carrierfrequency f1 of injected reception signal Sin1.

With the frequency locking detection block 25 shown in FIG. 2B, theoscillator 23 is variably controlled by the control block 24. Whetherfree-running oscillation frequency f2 of local oscillation signal S1 ofthe oscillator 23 has entered the frequency range up to injectionlocking to be frequency-locked with carrier frequency f1 of injectedreception signal Sin1 is determined. If the frequency locking is found,then enable signal SEN is generated. Enable signal SEN is divided intoLOCK indicative of signal logic that the frequency locking has beenfound and inverted LOCK (the upperline omitted here) indicative ofsignal logic that the frequency locking has not been found.

The frequency locking detection block 25 is composed of a frequencydiscriminator 51 and a comparator 52, for example. The frequencydiscriminator 51 converts a frequency variation of baseband signal SOUT1obtained by demodulating reception signal Sin1 into an amplitude value.Frequency-discriminated amplitude value is output to the comparator 52.The frequency discriminator 51 is connected with the comparator 52. Thecomparator 52 compares the amplitude value obtained from the frequencydiscriminator 51 with a preset comparison reference value to determinewhether free-running oscillation frequency f2 of the oscillator 23 hasbeen frequency-locked with carrier frequency f1 of injected receptionsignal Sin1. The comparison reference value is given by thresholdvoltage Vth output from an upper control system, for example.

If the amplitude value obtained from the frequency discriminator 51 isfound matching the preset comparison reference value, then thecomparator 52 outputs enable signal SEN=LOCK indicative of thecompletion of injection locking. If the amplitude value obtained fromthe frequency discriminator 51 is found not matching the presetcomparison reference value, then the comparator 52 outputs enable signalSEN=inverted LOCK (the upperline omitted here) indicative of theincompletion of injection locking. Enable signals SEN=LOCK and so on arealso output to the upper control system of the TRX2 on the receptionside in addition to the TRX1 on the transmission side.

Configuring the TRX2 as described above allows the frequency lockingdetection block 25 to detect the frequency locking of free-runningoscillation frequency f2 of local oscillation signal S1 of theoscillator 23 with carrier frequency f1 of injected reception signalSin1. If this frequency locking is found, the transmission section 22 isready for transmitting enable signal SEN generated by the frequencylocking detection block 25 to the TRX1 on the transmission side.

The following describes an exemplary relation between injected signaloutput value Ip and free-running oscillation frequency f2 with referenceto FIG. 3. The vertical axis shown in FIG. 3 is representative ofinjected signal output value Ip(dB). Injected signal output value Ipdenotes an intensity value of a beat signal that is obtained byinjecting reference carrier signal Sr having unmodulated carrierfrequency f1 into the oscillator 23 of the TRX2 as reception signal Sin1and entering reception signal Sin1 into the down-conversion mixer 203.

The beat signal denotes a signal indicative of a difference betweenreception signal Sin1 having carrier frequency f1 obtained from thedown-conversion mixer 203 and local oscillation signal S1 havingfree-running oscillation frequency f2 of the oscillator 23. Thehorizontal axis is representative of free-running oscillation frequencyf2 of the oscillator 23. For example, in the figure, free-runningoscillation frequency f2 is 59.6 GHz to 60.4 GHz, the scale being inunit of 0.2 GHz.

In this example, the relation between injected signal output value Ipand free-running oscillation frequency f2 is indicated by mostlyV-shaped characteristics curves. The characteristics curves are given byequation (1) below, namely:Ip(dB)=20·log 10{(2·α·Q·abs(f2−finj))/finj}  (1)where, f2 is free-running oscillation frequency of the oscillator 23, αis an amplitude of local oscillation signal S1 having free-runningoscillation frequency f2, Q (Quality factor) is a peak value of a tankcircuit of the oscillator 23, and finj is the center frequency of theoscillator 23 at the time of injection locking. In the graph, fabdenotes the frequency range of injection locking. In the figure, fa ofpoint a is representative of the lower-limit frequency while fb of pointb is representative of the upper-limit frequency. Frequency range fab isgiven by equation (2) below, namely:fab=½π·(ωinj±Δωm)Δωm=ρ·ω0/2αQ  (2)where center frequency finj of the oscillator 23 is replaced by ωinj,free-running oscillation frequency f2 is replaced by ω0, and theamplitude of reception signal Sin1 (injection signal) is ρ. Δωm isrepresentative of a frequency variation that is controlled by thecontrol block 24 within frequency range fab of injection locking.

The control block 24 controls free-running oscillation frequency f2 ofthe oscillator 23 to vary free-running oscillation frequency f2, therebylocking center frequency ωinj of frequency range fab of this injectionlocking with carrier frequency f1 of reception signal Sin1.

In this example, the output of the down-conversion mixer 203 in whichunmodulated reception signal Sin1 has been entered is a beat signal.This beat signal has injection signal output value Ip (dB) that is theintensity indicated by an almost quadratic curves if free-runningoscillation frequency f2 of local oscillation signal S1 of theoscillator 23 is outside the frequency range of carrier frequency f1 ofunmodulated reception signal Sin1. Further, the beat signal is a directcurrent having no injection signal output value Ip (dB) if free-runningoscillation frequency f2 is inside frequency range fab of carrierfrequency f1. In this example, frequency range fab at the time ofinjection locking in the oscillator 23 is 60 GHz+/−0.02 GHz.

The following describes a control example of free-running oscillationfrequency f2 with reference to FIGS. 4A and 4B. The vertical axis shownin FIG. 4A is representative of free-running oscillation frequency f2 ofthe oscillator 23. The horizontal axis is representative of time t atwhich injection locking is executed. In the figure, TRX2 receptionsignal is reception signal Sin1 received from the TRX1. tIL isrepresentative of a time up to frequency locking (injection locking).The TRX1 transmission signal shown in FIG. 4B is transmission signalSout1 to be transmitted from the TRX1 to the TRX2 and reception signalSin1 to be received by the TRX2. Reception signal Sin1 is injected inthe oscillator 23 as an injection signal.

In this example, the control block 24 sets free-running oscillationfrequency f2 to the oscillator 23 in injection locking control period#T1. Likewise, the control block 24 sets free-running oscillationfrequency f2=f2+Δ to the oscillator 23 in injection locking controlperiod #T2. The control block 24 sets free-running oscillation frequencyf2=f2+2Δ to the oscillator 23 in injection locking control period #T3.In this example, the oscillator 23 reaches the frequency locking at timetIL in injection locking control period #T3. It should be noted that, iffrequency locking cannot be obtained, free-running oscillation frequencyf2=f2+3Δ is set in injection locking control period #T4 indicated bydashed lines.

The following describes a first bidirectional wireless communicationmethod associated with present invention by way of a wirelesscommunication example in the first bidirectional wireless datatransmission system No. 1, with reference to FIGS. 5A and 5B. In thisembodiment, in the bidirectional wireless data transmission system No.1, the TRX2 is the wireless communication apparatus on the receptionside and the TRX1 is the wireless communication apparatus on thetransmission side. Free-running oscillation frequency f2 of localoscillation signal S1 of the oscillator 23 gets in the frequency rangeup to injection locking to be frequency-locked with carrier frequency f1of injected reception signal Sin1. If this frequency locking is detectedby the frequency locking detection block 25, it is assumed that the TRX2transmit enable signal SEN to the TRX1.

Under the above-mentioned wireless communication conditions at the timeof injection locking, the TRX2 gets, in step P21 shown in FIG. 5B, intoa reception state upon turning on of the up-counter 41 by the controlblock 24 shown in FIG. 2A. At this moment, the control block 24 shown inFIG. 2A controls free-running oscillation frequency f2 of the oscillator23. For example, let the injection locking control period shown in FIGS.5A and 5B be T and the injection locking control period shown in FIGS.4A and 4B be T=#T1, then free-running oscillation frequency f2 is set tothe oscillator 23 by injection locking control period T=#T1.

On one hand, in the TRX1, the transmission section 11 startstransmission in step P11. Next, in step P12, the TRX1 transmitstransmission signal Sout1 having unmodulated carrier frequency f1 to theTRX2 to execute request to connect processing. At this moment, the TRX1transmits, as transmission signal Sout1, reference carrier signal Srhaving predetermined unmodulated carrier frequency f1 without modulatingdata DIN1. Transmission signal Sout1 is radiated to the TRX2 via thetransmission antenna 106.

On the other hand, in step P22, the reception section 21 of the TRX2starts receiving reception signal Sin1. At this moment, the TRX2 injectsreception signal Sin1 having carrier frequency f1 received from the TRX1into the oscillator 23 and receives reception signal Sin1 while variablycontrolling free-running oscillation frequency f2 of the oscillator 23.Also, reception signal Sin1 is entered in the down-conversion mixer 203to be down-converted into baseband signal SOUT1. If transmission signalSout1 (=reception signal Sin1) transmitted from the TRX1 is unmodulated,a beat signal having a frequency that is a difference between carrierfrequency f1 and free-running oscillation frequency f2 is output fromthe down-conversion mixer 203. This beat signal is entered in thefrequency locking detection block 25.

Next, in step P23, the frequency locking detection block 25 determineswhether the oscillator 23 has been frequency-locked (injection-locked)by injection locking. At this moment, in the frequency locking detectionblock 25, the frequency discriminator 51 converts a frequency variationof baseband signal SOUT1 obtained by demodulating reception signal Sin1into an amplitude value. The amplitude value after frequencydiscrimination is output to the comparator 52. The comparator 52compares the amplitude value obtained from the frequency discriminator51 with a preset comparison reference value to determine whetherfree-running oscillation frequency f2 of the oscillator 23 has enteredthe frequency range up to injection locking to be frequency-locked withcarrier frequency f1 of injected reception signal Sin1. The comparisonreference value is given by threshold voltage Vth output from the uppercontrol system. If there is a mismatch between the amplitude valueobtained from the frequency discriminator 51 and the preset comparisonreference value, the comparator 52 outputs enable signal SEN=invertedLOCK (the upper line omitted here) to the control block 24.

In step P24, the control block 24 drives the up-counter 41. In step P25,the control block 24 sets free-running oscillation frequency f2=f2+Δ tothe oscillator 23. The oscillator 23 oscillates at free-runningoscillation frequency f2=f2+Δ during injection locking control periodT=#2. If the oscillator 23 has not reached frequency locking duringinjection locking control period T=#T2, the control block 24 drives theup-counter 41 again in step P24.

In step P25, the control block 24 sets free-running oscillationfrequency f2=f2+2Δ to the oscillator 23. The oscillator 23 oscillates atfree-running oscillation frequency f2=f2+2Δ during injection lockingcontrol period T=#T3. The control block 24 repeats the setting for theoscillator 23 to reach the frequency locking.

If carrier frequency f1 has entered frequency range fab of injectionlocking in step P25 mentioned above, the oscillator 23 isfrequency-locked with reference carrier signal Sr. When the oscillator23 has reached frequency locking, the output from the down-conversionmixer 203 becomes direct current. When the oscillator 23 has reachedfrequency locking, the amplitude value obtained from the frequencydiscriminator 51 matches the preset comparison reference value, so thatthe comparator 52 outputs enable signal SEN=LOCK indicative of thecompletion of injection locking. Enable signal SEN is entered in thecontrol block 24 to fix free-running oscillation frequency f2 of theoscillator 23. Center frequency ω0 of free-running oscillation frequencyf2 at this moment is generated by the oscillator 23. Enable signalsSEN=LOCK and so on are also output to the upper control system of theTRX2 on the reception side in addition to the TRX1 on the transmissionside.

If the oscillator 23 has reached frequency locking, then thetransmission section 22 turns on the modulation block 206 by use ofenable signal SEN as a trigger in step P26. The modulation block 206outputs modulated signal SIN2 obtained by modulating enable signal SENto the up-conversion mixer 208 via the baseband amplifier 207. Theup-conversion mixer 208 up-converts modulated signal SIN2 containingenable signal SEN on the basis of carrier signal Sr′ having carrierfrequency fr′ and outputs resultant Sout2. Carrier signal Sr′ is afrequency obtained by multiplying fixed free-running oscillationfrequency f2 by 2.

Next, in step P27, transmission signal Sout2 having carrier frequencyfr′ is transmitted from the TRX2 to the TRX1 to execute connectionacknowledge processing. At this moment, the transmission signal Sout2 isradiated to the TRX1 via the power amplifier 210 and the transmissionantenna 211. The reception antenna 107 of the TRX1 receives transmissionsignal Sout2 and outputs reception signal Sin2 containing enable signalSEN.

Receiving reception signal Sin2 containing enable signal SEN in stepP13, the TRX1 becomes ready for identifying (or recognizing) thatfrequency locking has been achieved between the TRX1 and the TRX2 andthe TRX1 can enter a communication state. Then, in step P14, the TRX1start communication of data DIN1 and so on. The TRX1 fixes carrierfrequency f1 to enter communication state. The TRX1 modulates data DIN1and up-converts modulated signal SIN1 containing modulated data DIN1 byreference carrier signal Sr having carrier frequency f1, therebytransmitting up-converted transmission signal Sout1 to the TRX2.

The reception antenna 201 of the TRX2 receives transmission signal Sout1containing data DIN1 and outputs reception signal Sin1 to the receptionsection 21. The reception section 21 receives reception signal Sin1 anddemodulates reception signal Sin1 in step P28, thereby reconstructingdata DOUT1. It should be noted that, in the case of a system having twoor more channels, the processing between TA and TB is repeated in stepP29.

As described above, according to the bidirectional wireless datatransmission system No. 1 as the first embodiment, the TRX1 multiplexesmodulated signal SIN1 obtained by modulating data DIN1 with referencecarrier signal Sr having predetermined carrier frequency f1, therebytransmitting resultant transmission signal Sout1. The TRX2 injectsreception signal Sin1 received from the TRX1 into the oscillator 23 and,at the same time, receives reception signal Sin1 while variablycontrolling free-running oscillation frequency f2 of the oscillator 23.

The TRX2 detects that free-running oscillation frequency f2 of theoscillator 23 has entered the frequency range up to injection locking tobe locked with carrier frequency f1 of injected reception signal Sin1,thereby generating enable signal SEN. If free-running oscillationfrequency f2 of the oscillator 23 is found frequency-locked with carrierfrequency f1 of injected reception signal Sin1, the TRX2 transmitsenable signal SEN to the TRX1.

Therefore, the TRX1 becomes ready for detecting (or recognizing) thatthe frequency locking with the TRX2 has been completed on the basis ofenable signal SEN and the TRX1 is in a communication enabled state.Consequently, transmitting data DIN1 and so on from the TRX1 to the TRX2after frequency locking allows the TRX2 to reconstruct data DOUT1 on thebasis of the signal of free-running oscillation frequency f2 afterfrequency locking.

Further, the oscillator 13 is sharably used between the transmissionsection 11 and the reception section 12 in the TRX1 and the oscillator23 is sharably used between the reception section 21 and thetransmission section 22 in the TRX2. This sharing can realize that, uponachieving of frequency locking by injection locking in the down-linksignal transmission system, frequency locking is automatically achievedalso in the up-link signal transmission channel in the reservedirection. Consequently, when data transmission is executed in theup-link signal transmission system, signal processing can be realized ina frequency-locked state.

Besides, as compared with a circuit that contains a PLL circuit, thefrequency locking circuit can be configured with a simpler circuit. Inaddition, if a free-running local oscillator in which free-runningoscillation frequency f2 has errors is used for the oscillator 23, theoscillation frequency of one side can be received by varying theoscillation frequency by the control block 24, thereby driving lockinginto the injection locking range. It should be noted that a down-countermay be used for the control block 24 instead of the up-counter 41.Obviously, the control block 24 may be configured by use of both theup-counter 41 and the down-counter.

The Second Embodiment

The following describes an exemplary configuration of a bidirectionalwireless data transmission system No. 2 practiced as a second embodimentof the invention with reference to FIG. 6. In the second embodiment, aTRX2′ has two or more different, two in this example, transmissionsections 22 and 26. Two uplink signal transmission channels areconfigured from the TRX2′ to the TRX1′. Carrier frequencies fr′ and fr″of the two uplink signal transmission channels are each generated by asingle oscillator 23 and on the basis of free-running oscillationfrequency f2. The TRX1′ has two reception sections 12 and 14.

Frequency relations between the transmission section 11 and thereception sections 12 and 14 in the TRX1′ are set to M/N (M and N areintegers). Frequency relations between the reception section 21 and thetransmission sections 22 and 26 in the TRX2′ are set to M/N (M and N areintegers). As shown in FIGS. 5A and 5B, in the bidirectional wirelessdata transmission system No. 2, the frequency locking based on injectionlocking between the TRX1′ and TRX2′ matches free-running oscillationfrequency f2 with carrier frequency f1. By use of this matching betweenfree-running oscillation frequency f2 and the carrier frequency f1, anoperation for placing frequency locking between two or more channels isrealized. This configuration allows the simultaneous realization of thefrequency locking of all uplink signal transmission channels.

The TRX2′ shown in FIG. 6 configures one example of the second wirelesscommunication apparatus and is composed of a reception section 21, afirst transmission section 22, an oscillator 23, a control block 24, afrequency locking detection block 25, a second transmission section 26,a reception antenna 201, and transmission antennas 211 and 217. Thetransmission section 22 configures the first uplink transmissionchannel. With reference to FIG. 6, components similar to thosepreviously described with reference to the first embodiment are denotedby the same reference characters and the description thereof will beskipped.

The second transmission section 26 configures the second uplink signaltransmission channel. As described before with reference to FIGS. 5A and5B, the frequency locking detection block 25 detects that free-runningoscillation frequency f2 has entered the frequency range up to injectionlocking to be frequency-locked with carrier frequency f1 of injectedreception signal Sin1. Then, after this injection locking, data DIN22 istransmitted to the TRX1′. The second transmission section 26 is composedof a modulation block 212, a baseband amplifier 213, an up-conversionmixer 214, a frequency multiplier 215, and a power amplifier 216.

The modulation block 212 receives data DIN22 and modulates this dataDIN22, outputting modulated signal SIN22. The modulation block 212 isconnected with the baseband amplifier 213. The baseband amplifier 213amplifies modulated signal SIN22. The baseband amplifier 213 isconnected with the up-conversion mixer 214. The up-conversion mixer 214and the oscillator 23 described before are connected with the frequencymultiplier 215. The frequency multiplier 215 outputs carrier frequencyfr″=3·f2 obtained by multiplying free-running oscillation frequency f2by 3 to the up-conversion mixer 214.

The up-conversion mixer 214 up-converts (multiplication processing forfrequency conversion) amplified modulated signal SIN22 and carriersignal Sr″ having carrier frequency fr″ to output transmission signalSout22. The up-conversion mixer 214 is connected with the poweramplifier 216. The power amplifier 216 amplifies up-convertedtransmission signal Sout22 and outputs amplified transmission signalSout22 to the antenna 217.

The antenna 217 receives transmission signal Sout22 and radiates thereceived signal in the form of electromagnetic waves. Consequently, thetransmission section 22 becomes ready for transmit transmission signalSout22 obtained by multiplexing modulated signal SIN22 after injectionlocking with carrier signal Sr″ having predetermined carrier frequencyfr″ to the communication mate TRX1′. It should be noted that, for thetransmission section 22, data DIN2, modulated signal SIN2, transmissionsignal Sout2, and so on shown in FIG. 1 should be replaced by dataDIN21, modulated signal SIN21, transmission signal Sout21, and so on,respectively.

In carrier frequency f1 in the transmission section 11 of the TRX1′ andcarrier frequency fr″ in the second transmission section 26 of the TRX2,relation M/N is set between carrier frequency f1 of the TRX1′ andcarrier frequency fr″=3·f1 of the TRX2′, where M and N are integers. Forexample, if carrier frequency f1 in the TRX1′ is set to 60 GHz, carrierfrequency fr″ in the TRX2′ is set to 180 GHz. In this example,f1:fr″=60:180=M:N (1:3).

Obviously, carrier signal Sr″ obtained by dividing local oscillationsignal S1 having free-running oscillation frequency f2 may be used. Forexample, if carrier frequency f1 in the TRX1′ is set to 60 GHz, carrierfrequency fr″ in the TRX2′ is set to 20 GHz. In this example,f1:fr″=60:20=M:N (3:1).

The TRX1′ configures one example of the first wireless communicationapparatus and is composed of a transmission section 11, an oscillator13, a first reception section 12, a second reception section 14, atransmission antenna 106, and reception antennas 107 and 113. The firstreception section 12 configures a first uplink signal transmissionchannel. With reference to FIG. 6, components similar to thosepreviously described with reference to the first embodiment are denotedby the same reference symbols and the description thereof will beskipped.

The second reception section 14 configures a second uplink signaltransmission channel and is composed of a low-noise amplifier 114, adown-conversion mixer 115, a frequency multiplier 116, a bandpass filter117, and a demodulator 118. The reception antenna 113 is connected withthe low-noise amplifier 114. The low-noise amplifier 114 amplifiesreception signal Sin22 received by the antenna 113. Reception signalSin22 contains carrier signal Sr″ three times as high as free-runningoscillation frequency f2. Reception signal Sin22 contains data DIN22transmitted from the TRX2′ after injection locking.

The low-noise amplifier 114 is connected with the down-conversion mixer115. The down-conversion mixer 115 is connected with frequencymultiplexer 116. The frequency multiplexer 116 is connected with theoscillator 13 to output 3×f1 local oscillation signal S1″ obtained bymultiplying carrier frequency f1 by 3 to the down-conversion mixer 115.The down-conversion mixer 115 down-converts (or subtracts) receptionsignal Sin22 on the basis of local oscillation signal S1″ output fromthe frequency multiplexer 116 and outputs a subtracted signal.

The down-conversion mixer 115 is connected with the bandpass filter 117.The bandpass filter 117 passes baseband signal SOUT22 containing dataDIN22 of the TRX2′ after injection locking. The bandpass filter 117 isconnected with the demodulator 118. The demodulator 118 demodulatesbaseband signal SOUT22 and outputs data DOUT22. It should be noted that,for the reception section 12, reception signal Sin2, baseband signalSOUT2, data DOUT1, and so on shown in FIG. 1 should be replaced byreception signal Sin21, baseband signal SOUT21, data DOUT21 and so on,respectively.

Exemplary operations of the bidirectional wireless data transmissionsystem No. 2 described above are as shown in FIGS. 5A and 5B up to theoperations to be executed until injection locking is provided betweenthe TRX1′ and the TRX2′. Upon injection locking, the first uplink signaltransmission channel and the second uplink signal transmission channelindependently execute wireless communication processing.

In the first uplink signal transmission channel, receiving data DIN21,the transmission section 22 of the TRX2′ outputs modulated signal SIN21obtained by modulated data DIN21 via the baseband amplifier 207 to theup conversion mixer 208. The up-conversion mixer 208 up-convertsmodulated signal SIN21 containing data DIN21 on the basis of carriersignal Sr′ having carrier frequency fr′ and outputs resultanttransmission signal Sout21. Carrier frequency Sr′ is a frequencyobtained by multiplying free-running oscillation frequency f2 by 2 inthe frequency multiplier 209.

Transmission signal Sout21 having carrier frequency fr′ is transmittedfrom the TRX2′ to the TRX1′. At this moment, transmission signal Sout21is radiated to the TRX1′ via the power amplifier 210 and thetransmission antenna 211. The reception antenna 107 of the TRX1′receives transmission signal Sout21 and outputs reception signal Sin21containing data DIN21. Receiving reception signal Sin21 containing dataDIN21, the TRX1′ demodulates reception signal Sin21, therebyreconstructing data DOUT21.

For the second uplink signal transmission channel, the secondtransmission section 26 outputs modulated signal SIN22 obtained bymodulating data DIN22 to the up-conversion mixer 214 via the basebandamplifier 213. The up-conversion mixer 214 up-converts modulated signalSIN22 containing data DIN22 on the basis of carrier signal Sr″ havingcarrier frequency fr″ and outputs resultant transmission signal Sout22.Carrier signal Sr″ is a frequency obtained by multiplying free-runningoscillation frequency f2 by 3 in the frequency multiplier 215.

Transmission signal Sout22 of the carrier frequency fr″ is transmittedfrom the TRX2′ to the TRX1′. At this moment, transmission signal Sout22is radiated to the TRX1′ via the power amplifier 216 and the antenna217. The antenna 113 of the TRX1′ receives transmission signal Sout22and radiates reception signal Sin22 containing data DIN22. Receivingreception signal Sin22 containing data DIN22, the TRX1′ demodulatesreception signal Sin22, thereby reconstructing data DOUT22.

As described above, according to the bidirectional wireless datatransmission system No. 2 practiced as the second embodiment of theinvention, the TRX2′ has two transmission sections 22 and 26 having twodifferent carrier frequencies fr′ and fr″ like carrier frequencies fr′and fr″ relative to free-running oscillation frequency f2. Two systemsof uplink signal transmission channels are configured from the TRX2′ tothe TRX1′. Carrier frequencies fr′ and fr″ of these uplink signaltransmission channels are generated by the single oscillator 23. TheTRX1′ has two reception sections 12 and 14.

Frequency relation between the transmission section 11 and the receptionsections 12 and 14 in the TRX1′ is set to relation M/N (M=3, N=1) like120 GHz and 180 GHz relative to carrier frequency f1=60 GHz. Frequencyrelation between the reception section 21 and the transmission sections22 and 26 in the TRX2′ is set to relation M/N (M=2, N=1) like 120 GHzand relation M/N (M=3, N=1) like 180 GHz relative to free-runningoscillation frequency f2=60 GHz.

Consequently, free-running oscillation frequency f2 comes to matchcarrier frequency f1 by the injection locking between the TRX1′ and theTRX2′, thereby realizing an operator for providing frequency lockingbetween the other two uplink signal transmission channels by use offree-running oscillation frequency f2 after injection locking. Thisallows wireless communication processing by simultaneous use of twosystems of uplink signal transmission channels after injection locking.

In addition, the oscillator 13 is sharably used between the transmissionsection 11 and the reception sections 12 and 14 in the TRX1′ and theoscillator 23 is sharably used between the reception section 21 and thetransmission sections 22 and 26 in the TRX2′. This sharing can easilyrealize automatic frequency locking between the two uplink signaltransmission channels in the reverse direction upon the establishment ofinjection locking.

The Third Embodiment

The following describes an exemplary configuration of a bidirectionalwireless data transmission system No. 3 practiced as a third embodimentof the invention with reference to FIG. 7. In the third embodiment, thecontrol block 24 described with reference to the first embodiment isarranged as a control block 84 in a TRX10. The control block 84multiplexes modulated signal SIN1 obtained by modulating data DIN1 byreference carrier signal Sr having predetermined carrier frequency f1and transmits resultant transmission signal Sout1. In this transmission,the control block 84 transmits transmission signal Sout1 while variablycontrolling carrier frequency f1 of reference carrier signal Sr on theside of the TRX10.

The bidirectional wireless data transmission system No. 3 shown in FIG.7 fast transmits signals in a millimeter band of frequencies 30 GHz to300 GHz for carrying movie images, computer graphics, and so on betweendevices arranged in proximity and inside a device. This system isapplicable asymmetrical wireless data transmission systems in whichdifferent carrier frequencies are used for transmission and reception torealize frequency locking by injection locking.

The bidirectional wireless data transmission system No. 3 has the TRX10and the TRX20. In this example, the TRX10 configures one example of athird wireless communication apparatus, thereby varying carrierfrequency f1 of the oscillator 13. Carrier frequency f1 concerned iscaptured into frequency range fab of injection locking of free-runningoscillation frequency f2 fixed by the oscillator 23 of the TRX20configuring one example of a fourth wireless communication apparatus.The TRX20 detects the frequency locking and signals in the millimeterband are transmitted and received by use of the detected frequencylocking as a trigger. Consequently, bidirectional frequency lockingstates can be confirmed.

The TRX10 is composed of a transmission section 11, a reception section12, the oscillator 13, the control block 84, a transmission antenna 106,and a reception antenna 107. The transmission section 11 multiplexesmodulated signal SIN1 obtained by modulated data DIN1 by referencecarrier signal Sr having predetermined carrier frequency f1 andtransmits resultant transmission signal Sout1 to the TRX20. In thistransmission, the TRX10 transmits transmission signal Sout1 whilevariably controlling carrier frequency f1 of reference carrier signalSr.

Like the first embodiment, the TRX20 is composed of a reception section21, a transmission section 22, an oscillator 23, a frequency lockingdetection block 85, a reception antenna 201, and a transmission antenna211. The TRX20 has the oscillator 23 that oscillates local oscillationsignal S1 having free-running oscillation frequency f2 (fixed). In thisexample, received reception signal Sin1 is injected in the oscillator23, but local oscillation signal S1 of the oscillator 23 is fixed.Free-running oscillation frequency f2 of the oscillator 23 is fixed inorder to vary carrier frequency f1 on the side of the TRX10.

The frequency locking detection block 85 gets baseband signal SOUT1obtained after down-conversion processing. For free-running oscillationfrequency f2 (fixed) of the oscillator 23, the frequency lockingdetection block 85 detects whether carrier frequency f1 of injectedreception signal Sin1 has entered a frequency range up to injectionlocking to be matched with free-running oscillation frequency f2concerned, thereby generating enable signal SEN. In this example, if thefrequency locking of carrier frequency f1 of injected reception signalSin1 with free-running oscillation frequency f2 of the oscillator 23 isfound, the TRX20 transmits enable signal SEN to the TRX10.

The reception section 12 of the TRX10 receives enable signal SEN fromthe TRX20 that has been output upon frequency locking of carrierfrequency f1 of injected reception signal Sin1 with free-runningoscillation frequency f2 of the oscillator 23 of the TRX 20. Withreference to FIG. 7, components similar to those previously describedwith reference to the first embodiment are denoted by the same referencesymbols and the description thereof will be skipped.

The following describes exemplary internal configurations of the controlblock 84 and the frequency locking detection block 85 with reference toFIGS. 8A and 8B. In order to variably control carrier frequency f1 ofthe oscillator 13, the control block 84 of the TRX10 is composed of anup-counter 41 and a digital/analog converter (hereafter referred to as aDA converter 42). The up-counter 41 up-counts the number of pulses ofclock signal CLK, for example, on the basis of start signal Start,thereby outputting oscillation control data Dc. The up-counter 41 stopsoutputting oscillation control data Dc on the basis of stop signal Stop.The up-counter 41 is connected with the DA converter 42.

The DA converter 42 digital-to-analog converts oscillation control dataDc to generate analog VCO control voltage Vc. VCO control voltage Vc isoutput to the oscillator 13 that generates reference carrier signal Sr.If VCO control voltage Vc gets higher than a certain reference voltage,the oscillator 13 decreases carrier frequency f1 of reference carriersignal Sr. If VCO control voltage Vc gets lower than a certain referencevoltage, the oscillator 13 increases carrier frequency f1 of referencecarrier signal Sr.

The control block 84 repeatedly increases or decreases carrier frequencyf1 of the oscillator 13 within a frequency range fab up to injectionlocking, thereby executing variable tuning. Consequently, the TRX20 canexecute, by injection control, frequency-control of free-runningoscillation frequency f2 (fixed) of the oscillator 23 in receptionsignal Sin1 has been injected. Configuring the TRX10 as described abovemakes carrier frequency f1 of injected reception signal Sin1 get in thefrequency range up to injection locking, thereby frequency-lockingcarrier frequency f1 with free-running oscillation frequency f2concerned in a remote operation manner. Injected reception signal Sin1has carrier frequency f1 for free-running oscillation frequency f2(fixed) of local oscillation signal S1 obtained through the oscillator23.

The exemplary internal configuration of the frequency locking detectionblock 85 shown in FIG. 8B is substantially the same as that of thefrequency locking detection block 85 shown in FIG. 2B, so that thedescription thereof will be skipped. In this example, the control block84 of the TRX10 variably controls carrier frequency f1 of referencecarrier signal Sr of the oscillator 13. Reference carrier signal Srhaving carrier frequency f1 to be variably controlled is injected in theoscillator 23 in the TRX20. The TRX20 determines whether carrierfrequency f1 of injected reception signal Sin1 has been frequency-lockedwith free-running oscillation frequency f2 (fixed) of the oscillator 23,thereby generating enable signal SEN. This enable signal SEN is asdescribed before with reference to the first embodiment of theinvention.

Configuring the TRX20 as described above allows the frequency locking offree-running oscillation frequency f2 (fixed) of the oscillator 23 withcarrier frequency f1 of injected reception signal Sin1 if carrierfrequency f1 is varied in the TRX10. If this frequency locking isdetected by the frequency locking detection block 85, the transmissionsection 22 can transmit enable signal SEN generated by the frequencylocking detection block 85 to the TRX10 on the transmission side.

The following describes exemplary wireless communication to be executedin the third bidirectional wireless data transmission system No. 3 withreference to FIGS. 9A and 9B. In this third embodiment, when frequencylocking based on injection locking is controlled, transmission signalSout1 is transmitted while variably controlling carrier frequency f1 ofreference carrier signal Sr. The TRX20 injects reception signal Sin1received from the TRX10 into the oscillator 23. AT this moment, it is apremise that the TRX20 determines whether carrier frequency f1 ofinjected reception signal Sin1 has been frequency-locked withfree-running oscillation frequency f2 (fixed) of the oscillator 23,thereby generating enable signal SEN.

Using these conditions as wireless communication conditions as describedabove at the time of injection locking, the control block 84 shown inFIG. 8A turns on the up-counter 41, upon which the TRX10 gets in areception state in step P31 shown in FIG. 9A. At this moment, thecontrol block 84 shown in FIG. 8A controls carrier frequency f1 of theoscillator 13. For example, let injection locking control period shownin FIG. 9A be T and injection locking control period shown in FIGS. 4Aand 4B be T=#T1, then carrier frequency f1 is set to the oscillator 13by injection locking control period T=#T1.

On the other hand, in step P41, the reception section 21 start receptionin the TRX20. Concurrently, in step P32, the transmission section 11 ofthe TRX10 starts transmitting transmission signal Sout1. In step P33,the TRX10 transmits transmission signal Sout1 having unmodulated carrierfrequency f1 to the TRX20, thereby executing request to connectprocessing. At this moment, the TRX10 transmits, as transmission signalSout1, reference carrier signal Sr having predetermined unmodulatedcarrier frequency f1 obtained from data DIN1 without modulation.Transmission signal Sout1 is radiated to the TRX20 via the transmissionantenna 106.

In step P42, the reception section 21 of the TRX20 receives receptionsignal Sin1. At this moment, the TRX20 injects reception signal Sin1having carrier frequency f1 received from the TRX10 into the oscillator23 and fixes free-running oscillation frequency f2 of the oscillator 23to receive reception signal Sin1. Also, reception signal Sin1 is enteredin the down-conversion mixer 203 to be down-converted, thereby beingfrequency-converted into baseband signal SOUT1. If transmission signalSout1 (=reception signal Sin1) from the TRX10 is unmodulated, a beatsignal having a frequency that is a difference between carrier frequencyf1 and free-running oscillation frequency f2 is output from thedown-conversion mixer 203. This beat signal is entered in the frequencylocking detection block 85.

Next, in step P43, the frequency locking detection block 85 determineswhether the oscillator 23 has been frequency-locked (orinjection-locked) due to injection locking. At this moment, in thefrequency locking detection block 85, a frequency discriminator 51converts a frequency variation of baseband signal SOUT1 obtained bydemodulating reception signal Sin1 into an amplitude value. Theamplitude value after frequency discrimination is output to a comparator52.

The comparator 52 compares the amplitude value obtained by the frequencydiscriminator 51 with a preset comparison reference value to determinewhether carrier frequency f1 of injected reception signal Sin1 has beenfrequency-locked with free-running oscillation frequency f2 (fixed) ofthe oscillator 23. The comparison reference value is given by thresholdvoltage Vth output from the upper control system. If there is a mismatchbetween the amplitude value obtained from the frequency discriminator 51and the comparison reference value, the comparator 52 outputs enablesignal SEN=inverted LOCK (the upperline omitted) indicative incompletionof injection locking to the upper control system.

In step P34, the control block 84 drives the up-counter 41. In step P35,the control block 84 sets free-running oscillation frequency f2=f2+Δ tothe oscillator 23. The oscillator 23 oscillates at free-runningoscillation frequency f2=f2+Δ during injection locking control periodT=#T2. If the oscillator 23 has not reached frequency locking duringinjection locking control period T=#T2, the control block 84 drives theup-counter 41 again in step P34.

In step P35, the control block 84 sets free-running oscillationfrequency f2=f2+2Δ to the oscillator 23. The oscillator 23 oscillates atfree-running oscillation frequency f2=f2+2Δ during injection lockingcontrol period T=#T3. The control block 84 repeats the setting for theoscillator 23 to reach frequency locking.

When carrier frequency f1 gets in frequency range fab of injectionlocking in step P35 above, the oscillator 23 frequency-locks withreference carrier signal Sr. When the oscillator 23 has reachedfrequency locking, the output from the down-conversion mixer 203 becomesdirect current. When the oscillator 23 has reached frequency locking,the amplitude value obtained from the frequency discriminator 51 matchesthe preset comparison reference value, so that the comparator 52 outputsenable signal SEN=LOCK indicative of completion of injection locking.Enable signal SEN is entered in the control block 84 of the TRX10 to fixcarrier frequency f1 of the oscillator 13. Center frequency ω0 ofcarrier frequency f1 at this moment is generated by the oscillator 13.Enable signals SEN=LOCK and so on are also output to the upper controlsystem of the TRX20 on the reception side in addition to the TRX10 onthe transmission side.

When the oscillator 23 has reached frequency locking, the transmissionsection 22 turns on the modulation block 206 by use of enable signal SENas a trigger in step P44. The modulation block 206 outputs modulatedsignal SIN2 obtained by modulating enable signal SEN to theup-conversion mixer 208 via the baseband amplifier 207. Theup-conversion mixer 208 up-converts modulated signal SIN2 containingenable signal SEN on the basis of carrier signal Sr′ having carrierfrequency fr′ and outputs resultant transmission signal Sout2. Carriersignal Sr′ has a frequency obtained by multiplying free-runningoscillation frequency f2 by 2 in the frequency multiplier 209.

Next, in step P45, transmission signal Sout2 having carrier frequencyfr′ is transmitted from the TRX20 to the TRX10 to execute connectionacknowledge. At this moment, transmission signal Sout2 is radiated tothe TRX10 via the power amplifier 210 and the transmission antenna 211.The reception antenna 107 of the TRX10 receives transmission signalSout2 and outputs reception signal Sin2 that contains enable signal SEN.

Receiving reception signal Sin2 containing enable signal SEN in stepS36, the TRX10 can identify (or recognize) that frequency locking hasbeen established between the TRX10 and the TRX20 and enter acommunication state thereafter. Next, communication of data DIN1 and soon is started in step P37 in the TRX10. The TRX10 fixes carrierfrequency f1 and enters the communication state. The TRX10 modulatesdata DIN1, up-converts modulated signal SIN1 containing modulated dataDIN1 by reference carrier signal Sr having carrier frequency f1, andtransmits up-converted transmission signal Sout1 to the TRX20.

The reception antenna 201 of the TRX20 receives transmission signalSout1 containing data DIN1 and outputs reception signal Sin1 to thereception section 21. The reception section 21 receives reception signalSin1 and demodulates reception signal Sin1 in step P46, therebyreconstructing data DOUT1.

As described above and according to the third bidirectional wirelessdata transmission system No. 3, the TRX10 multiplexes modulated signalSIN1 obtained by modulating data DIN1 by reference carrier signal Srhaving predetermined carrier signal f1 and transmits resultanttransmission signal Sout1. In this transmission, the TRX10 transmitstransmission signal Sout1 while variably controlling carrier frequencyf1 of reference carrier signal Sr.

The TRX20 injects reception signal Sin1 received from the TRX10 into theoscillator 23. At the same time, the TRX20 detects whether carrierfrequency f1 of injected reception signal Sin1 has entered the frequencyrange up to injection locking to be frequency-locked with self-runningoscillation frequency f2 concerned, thereby generating enable signalSEN. Reception signal Sin1 is variably controlled for free-runningoscillation frequency f2 (fixed) of the oscillator 23. If carrierfrequency f1 of injected reception signal Sin1 is found frequency-lockedwith free-running oscillation frequency f2 of the oscillator 23, thenthe TRX20 transmits enable signal SEN to the TRX10.

Therefore, the TRX10 can detect (or recognize) that frequency lockingwith the TRX20 has completed on the basis of enable signal SEN and knowthat TRX10 is communicable with the TRX20. Consequently, when data DIN1is transmitted from the TRX10 to the TRX20 after frequency locking, theTRX20 can reconstruct data DOUT1 on the basis of the signal offree-running oscillation frequency f2 after frequency locking. Besides,as compared with the circuit including a PLL circuit, the presentfrequency locking circuit according to the present embodiment can beconfigured with a simpler circuit.

In addition, if a free-running local oscillator in which free-runningoscillation frequency f2 has errors is used for the oscillator 23, theoscillation frequency of one side can be transmitted by varying theoscillation frequency by the control block 84, thereby driving lockinginto the injection locking range.

Further, returning enable signal SEN (or a message) indicative of theestablishment of frequency locking by injection locking from the TRX20to the TRX10 allows both the TRX20 and the TRX10 to recognize theestablishment of frequency locking, thereby shifting to a bidirectionalcommunication state.

In the TRX10, the oscillator 13 is sharably used between thetransmission section 11 and the reception section 12. In the TRX20, theoscillator 23 is sharably used between the reception section 21 and thetransmission section 22. This sharing can also easily realize automaticfrequency locking of the uplink signal transmission channel in thereverse direction upon the establishment of injection locking.

As described above, embodiments of the present invention are verysuitably applicable to wireless data transmission systems configured tofast transmit signals of millimeter band of which carrier frequency f1for carrying movie images, computer graphics, and so on ranges from 30GHz to 300 GHz. These wireless data transmission systems include digitalrecording/reproducing apparatuses, terrestrial-wave televisionreceivers, mobile telephones, game machines, computers, andcommunications apparatuses, for example.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2009-228003 filedin the Japan Patent Office on Sep. 30, 2009, the entire content of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A wireless communication apparatus forbidirectional wireless communication, comprising: a reception sectionconfigured to receive a wireless transmission signal and producetherefrom a reception signal; a first oscillator configured to produce asignal having a frequency upon which reception processing is based,where the reception signal is injected into the first oscillator; afrequency locking detection unit configured to detect whether thefrequency of the signal of the first oscillator is frequency locked witha carrier frequency of the reception signal, wherein, if the frequencylocking detection unit detects that oscillation frequency of the signalof the first oscillator is frequency-locked with the carrier frequencyof the reception signal, the wireless communication apparatus transmitsa communication enable signal; and a control unit, wherein the firstoscillator is configured to produce a signal having a free-runningoscillation frequency, and the control unit is configured to vary thefree-running oscillation frequency of the first oscillator.
 2. Thewireless communication apparatus of claim 1, further comprising at leastone transmission section configured to wirelessly transmit signals,wherein the at least one transmission section executes transmissionprocessing on the basis of a carrier signal obtained by multiplying thefrequency of the first oscillator after injection locking by apredetermined value.
 3. The wireless communication apparatus of claim 1,further comprising a plurality of transmission sections configured towirelessly transmit respective signals, wherein each of the plurality oftransmission sections executes transmission processing on the basis of adifferent carrier signal, each of the carrier signals of the pluralityof transmission sections being obtained by multiplying the frequency ofthe first oscillator after injection locking by a differentpredetermined value.
 4. The wireless communication apparatus of claim 1,wherein the reception section is configured to receive wireless signalsin the millimeter waveband.
 5. The wireless communication apparatus ofclaim 2, wherein the reception section is configured to receive wirelesssignals in the millimeter waveband and the at least one transmissionsection is configured to transmit signals in the millimeter waveband. 6.The wireless communication apparatus of claim 1, further comprising adown-converter unit configured to down-convert the reception signal onthe basis of the signal of the first oscillator and to output adown-converted signal, wherein the frequency locking detection unitcomprises a frequency discriminator that receives the down-convertedsignal as an input and outputs a frequency discriminated output value toa comparator, which compares the frequency discriminated output value toa threshold value, and wherein the frequency locking detection unitdetects that the free-running oscillation frequency of the signal of thefirst oscillator is frequency-locked with the carrier frequency of thereception signal when an output of the comparator changes.
 7. Thewireless communication apparatus of claim 1, further comprising at leastone transmission section configured to wirelessly transmit signals,wherein the at least one transmission section executes transmissionprocessing on the basis of a carrier signal obtained by multiplying thefree-running oscillation frequency of the first oscillator afterinjection locking by a predetermined value.
 8. The wirelesscommunication apparatus of claim 1, further comprising a plurality oftransmission sections configured to wirelessly transmit respectivesignals, wherein each of the plurality of transmission sections executestransmission processing on the basis of a different carrier signal, eachof the carrier signals of the plurality of transmission sections beingobtained by multiplying the free-running oscillation frequency of thefirst oscillator after injection locking by a different predeterminedvalue.
 9. The wireless communication apparatus of claim 1, wherein thecontrol unit is configured to vary the free-running oscillationfrequency of the first oscillator such that the frequency of the firstoscillator is periodically incremented by a predetermined amount at apredetermined period until the frequency locking detection unit detectsthat the free-running oscillation frequency of the signal of the firstoscillator is frequency-locked with the carrier frequency of thereception signal.
 10. A wireless communication apparatus, comprising:reception means for receiving a wireless transmission signal andproducing therefrom a reception signal; first oscillation means forproducing a signal having a frequency upon which reception processing isbased, where the reception signal is injected into the first oscillationmeans; frequency locking detection means for detecting whether thefrequency of the signal of the first oscillation means is frequencylocked with a carrier frequency of the reception signal, wherein, if thefrequency locking detection means detects that the frequency of thesignal of the first oscillation means is frequency-locked with thecarrier frequency of the reception signal, the wireless communicationapparatus transmits a communication enable signal; and a control means,wherein first oscillation means produces a signal having a free-runningoscillation frequency, and the control means varies the free-runningoscillation frequency of the first oscillator.
 11. A method ofbidirectional wireless communication via a wireless communicationapparatus comprising: prior to beginning communication of data via thewireless communication apparatus, performing an injection lockingcontrol process comprising: wirelessly receiving a transmission signaland generating therefrom a reception signal, injecting the receptionsignal into a first oscillator whose frequency is used for receptionprocessing, determining whether the frequency of the first oscillator isfrequency locked with a carrier frequency of the reception signal, ifthe frequency of the signal of the first oscillator is frequency-lockedwith the carrier frequency of the reception signal, transmitting acommunication enable signal, wherein the first oscillator has afree-running oscillation frequency, and varying a frequency of the firstoscillator until the frequency of the signal of the first oscillator isfrequency-locked with the carrier frequency of the reception signal; andbeginning communication of data via the wireless communication apparatusonly after the enable signal has been transmitted.
 12. A non-transitorycomputer readable medium having program code stored thereon, the programcode being executable by a processor to cause the processor to issuecommands to control bidirectional wireless communication of a wirelesscommunication apparatus such that: prior to beginning communication ofdata, the wireless communication apparatus performs an injection lockingcontrol process comprising: wirelessly receiving a transmission signaland generating therefrom a reception signal, injecting the receptionsignal into a first oscillator whose frequency is used for receptionprocessing, determining whether the frequency of the first oscillator isfrequency locked with a carrier frequency of the reception signal, andif the frequency of the signal of the first oscillator isfrequency-locked with the carrier frequency of the reception signal,transmitting a communication enable signal; and the wirelesscommunication apparatus begins communication of data only after theenable signal has been transmitted, wherein the first oscillator has afree-running oscillation frequency, and the program code is executableby the processor to cause the processor to issue commands to controlbidirectional wireless communication of the wireless communicationapparatus such that the wireless communication apparatus varies afrequency of the first oscillator until the frequency of the signal ofthe first oscillator is frequency-locked with the carrier frequency ofthe reception signal.
 13. The wireless communication apparatus of claim10, further comprising at least one transmission section configured towirelessly transmit signals, wherein the at least one transmissionsection executes transmission processing on the basis of a carriersignal obtained by multiplying the frequency of the first oscillatorafter injection locking by a predetermined value.
 14. The wirelesscommunication apparatus of claim 10, further comprising a plurality oftransmission sections configured to wirelessly transmit respectivesignals, wherein each of the plurality of transmission sections executestransmission processing on the basis of a different carrier signal, eachof the carrier signals of the plurality of transmission sections beingobtained by multiplying the frequency of the first oscillator afterinjection locking by a different predetermined value.
 15. The wirelesscommunication apparatus of claim 10, wherein the reception section isconfigured to receive wireless signals in the millimeter waveband. 16.The wireless communication apparatus of claim 13, wherein the receptionsection is configured to receive wireless signals in the millimeterwaveband and the at least one transmission section is configured totransmit signals in the millimeter waveband.
 17. The method of claim 11,wherein at least one transmission section is configured to wirelesslytransmit signals, and the at least one transmission section executestransmission processing on the basis of a carrier signal obtained bymultiplying the frequency of the first oscillator after injectionlocking by a predetermined value.
 18. The method of claim 11, wherein aplurality of transmission sections are configured to wirelessly transmitrespective signals, and each of the plurality of transmission sectionsexecutes transmission processing on the basis of a different carriersignal, each of the carrier signals of the plurality of transmissionsections being obtained by multiplying the frequency of the firstoscillator after injection locking by a different predetermined value.19. The method of claim 11, wherein the reception section is configuredto receive wireless signals in the millimeter waveband.
 20. The methodof claim 17, wherein the reception section is configured to receivewireless signals in the millimeter waveband and the at least onetransmission section is configured to transmit signals in the millimeterwaveband.
 21. The computer readable medium of claim 12, wherein at leastone transmission section is configured to wirelessly transmit signals,and the at least one transmission section executes transmissionprocessing on the basis of a carrier signal obtained by multiplying thefrequency of the first oscillator after injection locking by apredetermined value.
 22. The computer readable medium of claim 12,wherein a plurality of transmission sections are configured towirelessly transmit respective signals, and each of the plurality oftransmission sections executes transmission processing on the basis of adifferent carrier signal, each of the carrier signals of the pluralityof transmission sections being obtained by multiplying the frequency ofthe first oscillator after injection locking by a differentpredetermined value.
 23. The computer readable medium of claim 12,wherein the reception section is configured to receive wireless signalsin the millimeter waveband.
 24. The computer readable medium of claim21, wherein the reception section is configured to receive wirelesssignals in the millimeter waveband and the at least one transmissionsection is configured to transmit signals in the millimeter waveband.